register_post_type

The timeline below displays how wordpress function register_post_type has changed across different WordPress versions. If a version is not listed, refer to the next available version below.

WordPress Version: 6.5

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of `WP_Post_Type`.
 * @since 4.7.0 Introduced `show_in_rest`, `rest_base` and `rest_controller_class`
 *              arguments to register the post type in REST API.
 * @since 5.0.0 The `template` and `template_lock` arguments were added.
 * @since 5.3.0 The `supports` argument will now accept an array of arguments for a feature.
 * @since 5.9.0 The `rest_namespace` argument was added.
 *
 * @global array $wp_post_types List of post types.
 *
 * @param string       $post_type Post type key. Must not exceed 20 characters and may only contain
 *                                lowercase alphanumeric characters, dashes, and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string       $label                           Name of the post type shown in the menu. Usually plural.
 *                                                         Default is value of $labels['name'].
 *     @type string[]     $labels                          An array of labels for this post type. If not set, post
 *                                                         labels are inherited for non-hierarchical types and page
 *                                                         labels for hierarchical ones. See get_post_type_labels() for a full
 *                                                         list of supported labels.
 *     @type string       $description                     A short descriptive summary of what the post type is.
 *                                                         Default empty.
 *     @type bool         $public                          Whether a post type is intended for use publicly either via
 *                                                         the admin interface or by front-end users. While the default
 *                                                         settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                                         and $show_in_nav_menus are inherited from $public, each does not
 *                                                         rely on this relationship and controls a very specific intention.
 *                                                         Default false.
 *     @type bool         $hierarchical                    Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool         $exclude_from_search             Whether to exclude posts with this post type from front end search
 *                                                         results. Default is the opposite value of $public.
 *     @type bool         $publicly_queryable              Whether queries can be performed on the front end for the post type
 *                                                         as part of parse_request(). Endpoints would include:
 *                                                          * ?post_type={post_type_key}
 *                                                          * ?{post_type_key}={single_post_slug}
 *                                                          * ?{post_type_query_var}={single_post_slug}
 *                                                         If not set, the default is inherited from $public.
 *     @type bool         $show_ui                         Whether to generate and allow a UI for managing this post type in the
 *                                                         admin. Default is value of $public.
 *     @type bool|string  $show_in_menu                    Where to show the post type in the admin menu. To work, $show_ui
 *                                                         must be true. If true, the post type is shown in its own top level
 *                                                         menu. If false, no menu is shown. If a string of an existing top
 *                                                         level menu ('tools.php' or 'edit.php?post_type=page', for example), the
 *                                                         post type will be placed as a sub-menu of that.
 *                                                         Default is value of $show_ui.
 *     @type bool         $show_in_nav_menus               Makes this post type available for selection in navigation menus.
 *                                                         Default is value of $public.
 *     @type bool         $show_in_admin_bar               Makes this post type available via the admin bar. Default is value
 *                                                         of $show_in_menu.
 *     @type bool         $show_in_rest                    Whether to include the post type in the REST API. Set this to true
 *                                                         for the post type to be available in the block editor.
 *     @type string       $rest_base                       To change the base URL of REST API route. Default is $post_type.
 *     @type string       $rest_namespace                  To change the namespace URL of REST API route. Default is wp/v2.
 *     @type string       $rest_controller_class           REST API controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type string|bool  $autosave_rest_controller_class  REST API controller class name. Default is 'WP_REST_Autosaves_Controller'.
 *     @type string|bool  $revisions_rest_controller_class REST API controller class name. Default is 'WP_REST_Revisions_Controller'.
 *     @type bool         $late_route_registration         A flag to direct the REST API controllers for autosave / revisions
 *                                                         should be registered before/after the post type controller.
 *     @type int          $menu_position                   The position in the menu order the post type should appear. To work,
 *                                                         $show_in_menu must be true. Default null (at the bottom).
 *     @type string       $menu_icon                       The URL to the icon to be used for this menu. Pass a base64-encoded
 *                                                         SVG using a data URI, which will be colored to match the color scheme
 *                                                         -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                                         of a Dashicons helper class to use a font icon, e.g.
 *                                                        'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                                         so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string|array $capability_type                 The string to use to build the read, edit, and delete capabilities.
 *                                                         May be passed as an array to allow for alternative plurals when using
 *                                                         this argument as a base to construct the capabilities, e.g.
 *                                                         array('story', 'stories'). Default 'post'.
 *     @type string[]     $capabilities                    Array of capabilities for this post type. $capability_type is used
 *                                                         as a base to construct capabilities by default.
 *                                                         See get_post_type_capabilities().
 *     @type bool         $map_meta_cap                    Whether to use the internal default meta capability handling.
 *                                                         Default false.
 *     @type array|false  $supports                        Core feature(s) the post type supports. Serves as an alias for calling
 *                                                         add_post_type_support() directly. Core features include 'title',
 *                                                         'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                                         'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                                         Additionally, the 'revisions' feature dictates whether the post type
 *                                                         will store revisions, and the 'comments' feature dictates whether the
 *                                                         comments count will show on the edit screen. A feature can also be
 *                                                         specified as an array of arguments to provide additional information
 *                                                         about supporting that feature.
 *                                                         Example: `array( 'my_feature', array( 'field' => 'value' ) )`.
 *                                                         If false, no features will be added.
 *                                                         Default is an array containing 'title' and 'editor'.
 *     @type callable     $register_meta_box_cb            Provide a callback function that sets up the meta boxes for the
 *                                                         edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                                         callback. Default null.
 *     @type string[]     $taxonomies                      An array of taxonomy identifiers that will be registered for the
 *                                                         post type. Taxonomies can be registered later with register_taxonomy()
 *                                                         or register_taxonomy_for_object_type().
 *                                                         Default empty array.
 *     @type bool|string  $has_archive                     Whether there should be post type archives, or if a string, the
 *                                                         archive slug to use. Will generate the proper rewrite rules if
 *                                                         $rewrite is enabled. Default false.
 *     @type bool|array   $rewrite                         {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type int    $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool  $query_var                      Sets the query_var key for this post type. Defaults to $post_type
 *                                                        key. If false, a post type cannot be loaded at
 *                                                        ?{query_var}={post_slug}. If specified as a string, the query
 *                                                        ?{query_var_string}={post_slug} will be valid.
 *     @type bool         $can_export                     Whether to allow this post type to be exported. Default true.
 *     @type bool         $delete_with_user               Whether to delete posts of this type when deleting a user.
 *                                                          * If true, posts of this type belonging to the user will be moved
 *                                                            to Trash when the user is deleted.
 *                                                          * If false, posts of this type belonging to the user will *not*
 *                                                            be trashed or deleted.
 *                                                          * If not set (the default), posts are trashed if post type supports
 *                                                            the 'author' feature. Otherwise posts are not trashed or deleted.
 *                                                        Default null.
 *     @type array        $template                       Array of blocks to use as the default initial state for an editor
 *                                                        session. Each item should be an array containing block name and
 *                                                        optional attributes. Default empty array.
 *     @type string|false $template_lock                  Whether the block template should be locked if $template is set.
 *                                                        * If set to 'all', the user is unable to insert new blocks,
 *                                                          move existing blocks and delete blocks.
 *                                                       * If set to 'insert', the user is able to move existing blocks
 *                                                         but is unable to insert new blocks and delete blocks.
 *                                                         Default false.
 *     @type bool         $_builtin                     FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                                      "built-in" post_type. Default false.
 *     @type string       $_edit_link                   FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                                      this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object on success,
 *                               WP_Error object on failure.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name.
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a `WP_Post_Type` object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    /**
     * Fires after a specific post type is registered.
     *
     * The dynamic portion of the filter name, `$post_type`, refers to the post type key.
     *
     * Possible hook names include:
     *
     *  - `registered_post_type_post`
     *  - `registered_post_type_page`
     *
     * @since 6.0.0
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action("registered_post_type_{$post_type}", $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 6.4

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of `WP_Post_Type`.
 * @since 4.7.0 Introduced `show_in_rest`, `rest_base` and `rest_controller_class`
 *              arguments to register the post type in REST API.
 * @since 5.0.0 The `template` and `template_lock` arguments were added.
 * @since 5.3.0 The `supports` argument will now accept an array of arguments for a feature.
 * @since 5.9.0 The `rest_namespace` argument was added.
 *
 * @global array $wp_post_types List of post types.
 *
 * @param string       $post_type Post type key. Must not exceed 20 characters and may only contain
 *                                lowercase alphanumeric characters, dashes, and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string       $label                           Name of the post type shown in the menu. Usually plural.
 *                                                         Default is value of $labels['name'].
 *     @type string[]     $labels                          An array of labels for this post type. If not set, post
 *                                                         labels are inherited for non-hierarchical types and page
 *                                                         labels for hierarchical ones. See get_post_type_labels() for a full
 *                                                         list of supported labels.
 *     @type string       $description                     A short descriptive summary of what the post type is.
 *                                                         Default empty.
 *     @type bool         $public                          Whether a post type is intended for use publicly either via
 *                                                         the admin interface or by front-end users. While the default
 *                                                         settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                                         and $show_in_nav_menus are inherited from $public, each does not
 *                                                         rely on this relationship and controls a very specific intention.
 *                                                         Default false.
 *     @type bool         $hierarchical                    Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool         $exclude_from_search             Whether to exclude posts with this post type from front end search
 *                                                         results. Default is the opposite value of $public.
 *     @type bool         $publicly_queryable              Whether queries can be performed on the front end for the post type
 *                                                         as part of parse_request(). Endpoints would include:
 *                                                          * ?post_type={post_type_key}
 *                                                          * ?{post_type_key}={single_post_slug}
 *                                                          * ?{post_type_query_var}={single_post_slug}
 *                                                         If not set, the default is inherited from $public.
 *     @type bool         $show_ui                         Whether to generate and allow a UI for managing this post type in the
 *                                                         admin. Default is value of $public.
 *     @type bool|string  $show_in_menu                    Where to show the post type in the admin menu. To work, $show_ui
 *                                                         must be true. If true, the post type is shown in its own top level
 *                                                         menu. If false, no menu is shown. If a string of an existing top
 *                                                         level menu ('tools.php' or 'edit.php?post_type=page', for example), the
 *                                                         post type will be placed as a sub-menu of that.
 *                                                         Default is value of $show_ui.
 *     @type bool         $show_in_nav_menus               Makes this post type available for selection in navigation menus.
 *                                                         Default is value of $public.
 *     @type bool         $show_in_admin_bar               Makes this post type available via the admin bar. Default is value
 *                                                         of $show_in_menu.
 *     @type bool         $show_in_rest                    Whether to include the post type in the REST API. Set this to true
 *                                                         for the post type to be available in the block editor.
 *     @type string       $rest_base                       To change the base URL of REST API route. Default is $post_type.
 *     @type string       $rest_namespace                  To change the namespace URL of REST API route. Default is wp/v2.
 *     @type string       $rest_controller_class           REST API controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type string|bool  $autosave_rest_controller_class  REST API controller class name. Default is 'WP_REST_Autosaves_Controller'.
 *     @type string|bool  $revisions_rest_controller_class REST API controller class name. Default is 'WP_REST_Revisions_Controller'.
 *     @type bool         $late_route_registration         A flag to direct the REST API controllers for autosave / revisions should be registered before/after the post type controller.
 *     @type int          $menu_position                   The position in the menu order the post type should appear. To work,
 *                                                         $show_in_menu must be true. Default null (at the bottom).
 *     @type string       $menu_icon                       The URL to the icon to be used for this menu. Pass a base64-encoded
 *                                                         SVG using a data URI, which will be colored to match the color scheme
 *                                                         -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                                         of a Dashicons helper class to use a font icon, e.g.
 *                                                        'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                                         so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string|array $capability_type                 The string to use to build the read, edit, and delete capabilities.
 *                                                         May be passed as an array to allow for alternative plurals when using
 *                                                         this argument as a base to construct the capabilities, e.g.
 *                                                         array('story', 'stories'). Default 'post'.
 *     @type string[]     $capabilities                    Array of capabilities for this post type. $capability_type is used
 *                                                         as a base to construct capabilities by default.
 *                                                         See get_post_type_capabilities().
 *     @type bool         $map_meta_cap                    Whether to use the internal default meta capability handling.
 *                                                         Default false.
 *     @type array        $supports                        Core feature(s) the post type supports. Serves as an alias for calling
 *                                                         add_post_type_support() directly. Core features include 'title',
 *                                                         'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                                         'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                                         Additionally, the 'revisions' feature dictates whether the post type
 *                                                         will store revisions, and the 'comments' feature dictates whether the
 *                                                         comments count will show on the edit screen. A feature can also be
 *                                                         specified as an array of arguments to provide additional information
 *                                                         about supporting that feature.
 *                                                         Example: `array( 'my_feature', array( 'field' => 'value' ) )`.
 *                                                         Default is an array containing 'title' and 'editor'.
 *     @type callable     $register_meta_box_cb            Provide a callback function that sets up the meta boxes for the
 *                                                         edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                                         callback. Default null.
 *     @type string[]     $taxonomies                      An array of taxonomy identifiers that will be registered for the
 *                                                         post type. Taxonomies can be registered later with register_taxonomy()
 *                                                         or register_taxonomy_for_object_type().
 *                                                         Default empty array.
 *     @type bool|string  $has_archive                     Whether there should be post type archives, or if a string, the
 *                                                         archive slug to use. Will generate the proper rewrite rules if
 *                                                         $rewrite is enabled. Default false.
 *     @type bool|array   $rewrite                         {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type int    $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool  $query_var                      Sets the query_var key for this post type. Defaults to $post_type
 *                                                        key. If false, a post type cannot be loaded at
 *                                                        ?{query_var}={post_slug}. If specified as a string, the query
 *                                                        ?{query_var_string}={post_slug} will be valid.
 *     @type bool         $can_export                     Whether to allow this post type to be exported. Default true.
 *     @type bool         $delete_with_user               Whether to delete posts of this type when deleting a user.
 *                                                          * If true, posts of this type belonging to the user will be moved
 *                                                            to Trash when the user is deleted.
 *                                                          * If false, posts of this type belonging to the user will *not*
 *                                                            be trashed or deleted.
 *                                                          * If not set (the default), posts are trashed if post type supports
 *                                                            the 'author' feature. Otherwise posts are not trashed or deleted.
 *                                                        Default null.
 *     @type array        $template                       Array of blocks to use as the default initial state for an editor
 *                                                        session. Each item should be an array containing block name and
 *                                                        optional attributes. Default empty array.
 *     @type string|false $template_lock                  Whether the block template should be locked if $template is set.
 *                                                        * If set to 'all', the user is unable to insert new blocks,
 *                                                          move existing blocks and delete blocks.
 *                                                       * If set to 'insert', the user is able to move existing blocks
 *                                                         but is unable to insert new blocks and delete blocks.
 *                                                         Default false.
 *     @type bool         $_builtin                     FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                                      "built-in" post_type. Default false.
 *     @type string       $_edit_link                   FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                                      this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object on success,
 *                               WP_Error object on failure.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name.
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a `WP_Post_Type` object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    /**
     * Fires after a specific post type is registered.
     *
     * The dynamic portion of the filter name, `$post_type`, refers to the post type key.
     *
     * Possible hook names include:
     *
     *  - `registered_post_type_post`
     *  - `registered_post_type_page`
     *
     * @since 6.0.0
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action("registered_post_type_{$post_type}", $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 6.2

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of `WP_Post_Type`.
 * @since 4.7.0 Introduced `show_in_rest`, `rest_base` and `rest_controller_class`
 *              arguments to register the post type in REST API.
 * @since 5.0.0 The `template` and `template_lock` arguments were added.
 * @since 5.3.0 The `supports` argument will now accept an array of arguments for a feature.
 * @since 5.9.0 The `rest_namespace` argument was added.
 *
 * @global array $wp_post_types List of post types.
 *
 * @param string       $post_type Post type key. Must not exceed 20 characters and may only contain
 *                                lowercase alphanumeric characters, dashes, and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string       $label                 Name of the post type shown in the menu. Usually plural.
 *                                               Default is value of $labels['name'].
 *     @type string[]     $labels                An array of labels for this post type. If not set, post
 *                                               labels are inherited for non-hierarchical types and page
 *                                               labels for hierarchical ones. See get_post_type_labels() for a full
 *                                               list of supported labels.
 *     @type string       $description           A short descriptive summary of what the post type is.
 *                                               Default empty.
 *     @type bool         $public                Whether a post type is intended for use publicly either via
 *                                               the admin interface or by front-end users. While the default
 *                                               settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                               and $show_in_nav_menus are inherited from $public, each does not
 *                                               rely on this relationship and controls a very specific intention.
 *                                               Default false.
 *     @type bool         $hierarchical          Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool         $exclude_from_search   Whether to exclude posts with this post type from front end search
 *                                               results. Default is the opposite value of $public.
 *     @type bool         $publicly_queryable    Whether queries can be performed on the front end for the post type
 *                                               as part of parse_request(). Endpoints would include:
 *                                               * ?post_type={post_type_key}
 *                                               * ?{post_type_key}={single_post_slug}
 *                                               * ?{post_type_query_var}={single_post_slug}
 *                                               If not set, the default is inherited from $public.
 *     @type bool         $show_ui               Whether to generate and allow a UI for managing this post type in the
 *                                               admin. Default is value of $public.
 *     @type bool|string  $show_in_menu          Where to show the post type in the admin menu. To work, $show_ui
 *                                               must be true. If true, the post type is shown in its own top level
 *                                               menu. If false, no menu is shown. If a string of an existing top
 *                                               level menu ('tools.php' or 'edit.php?post_type=page', for example), the
 *                                               post type will be placed as a sub-menu of that.
 *                                               Default is value of $show_ui.
 *     @type bool         $show_in_nav_menus     Makes this post type available for selection in navigation menus.
 *                                               Default is value of $public.
 *     @type bool         $show_in_admin_bar     Makes this post type available via the admin bar. Default is value
 *                                               of $show_in_menu.
 *     @type bool         $show_in_rest          Whether to include the post type in the REST API. Set this to true
 *                                               for the post type to be available in the block editor.
 *     @type string       $rest_base             To change the base URL of REST API route. Default is $post_type.
 *     @type string       $rest_namespace        To change the namespace URL of REST API route. Default is wp/v2.
 *     @type string       $rest_controller_class REST API controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type int          $menu_position         The position in the menu order the post type should appear. To work,
 *                                               $show_in_menu must be true. Default null (at the bottom).
 *     @type string       $menu_icon             The URL to the icon to be used for this menu. Pass a base64-encoded
 *                                               SVG using a data URI, which will be colored to match the color scheme
 *                                               -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                               of a Dashicons helper class to use a font icon, e.g.
 *                                               'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                               so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string|array $capability_type       The string to use to build the read, edit, and delete capabilities.
 *                                               May be passed as an array to allow for alternative plurals when using
 *                                               this argument as a base to construct the capabilities, e.g.
 *                                               array('story', 'stories'). Default 'post'.
 *     @type string[]     $capabilities          Array of capabilities for this post type. $capability_type is used
 *                                               as a base to construct capabilities by default.
 *                                               See get_post_type_capabilities().
 *     @type bool         $map_meta_cap          Whether to use the internal default meta capability handling.
 *                                               Default false.
 *     @type array        $supports              Core feature(s) the post type supports. Serves as an alias for calling
 *                                               add_post_type_support() directly. Core features include 'title',
 *                                               'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                               'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                               Additionally, the 'revisions' feature dictates whether the post type
 *                                               will store revisions, and the 'comments' feature dictates whether the
 *                                               comments count will show on the edit screen. A feature can also be
 *                                               specified as an array of arguments to provide additional information
 *                                               about supporting that feature.
 *                                               Example: `array( 'my_feature', array( 'field' => 'value' ) )`.
 *                                               Default is an array containing 'title' and 'editor'.
 *     @type callable     $register_meta_box_cb  Provide a callback function that sets up the meta boxes for the
 *                                               edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                               callback. Default null.
 *     @type string[]     $taxonomies            An array of taxonomy identifiers that will be registered for the
 *                                               post type. Taxonomies can be registered later with register_taxonomy()
 *                                               or register_taxonomy_for_object_type().
 *                                               Default empty array.
 *     @type bool|string  $has_archive           Whether there should be post type archives, or if a string, the
 *                                               archive slug to use. Will generate the proper rewrite rules if
 *                                               $rewrite is enabled. Default false.
 *     @type bool|array   $rewrite               {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type int    $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool  $query_var             Sets the query_var key for this post type. Defaults to $post_type
 *                                               key. If false, a post type cannot be loaded at
 *                                               ?{query_var}={post_slug}. If specified as a string, the query
 *                                               ?{query_var_string}={post_slug} will be valid.
 *     @type bool         $can_export            Whether to allow this post type to be exported. Default true.
 *     @type bool         $delete_with_user      Whether to delete posts of this type when deleting a user.
 *                                               * If true, posts of this type belonging to the user will be moved
 *                                                 to Trash when the user is deleted.
 *                                               * If false, posts of this type belonging to the user will *not*
 *                                                 be trashed or deleted.
 *                                               * If not set (the default), posts are trashed if post type supports
 *                                                 the 'author' feature. Otherwise posts are not trashed or deleted.
 *                                               Default null.
 *     @type array        $template              Array of blocks to use as the default initial state for an editor
 *                                               session. Each item should be an array containing block name and
 *                                               optional attributes. Default empty array.
 *     @type string|false $template_lock         Whether the block template should be locked if $template is set.
 *                                               * If set to 'all', the user is unable to insert new blocks,
 *                                                 move existing blocks and delete blocks.
 *                                               * If set to 'insert', the user is able to move existing blocks
 *                                                 but is unable to insert new blocks and delete blocks.
 *                                               Default false.
 *     @type bool         $_builtin              FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                               "built-in" post_type. Default false.
 *     @type string       $_edit_link            FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                               this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object on success,
 *                               WP_Error object on failure.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name.
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a `WP_Post_Type` object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    /**
     * Fires after a specific post type is registered.
     *
     * The dynamic portion of the filter name, `$post_type`, refers to the post type key.
     *
     * Possible hook names include:
     *
     *  - `registered_post_type_post`
     *  - `registered_post_type_page`
     *
     * @since 6.0.0
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action("registered_post_type_{$post_type}", $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 6.1

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of `WP_Post_Type`.
 * @since 4.7.0 Introduced `show_in_rest`, `rest_base` and `rest_controller_class`
 *              arguments to register the post type in REST API.
 * @since 5.0.0 The `template` and `template_lock` arguments were added.
 * @since 5.3.0 The `supports` argument will now accept an array of arguments for a feature.
 * @since 5.9.0 The `rest_namespace` argument was added.
 *
 * @global array $wp_post_types List of post types.
 *
 * @param string       $post_type Post type key. Must not exceed 20 characters and may
 *                                only contain lowercase alphanumeric characters, dashes,
 *                                and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string       $label                 Name of the post type shown in the menu. Usually plural.
 *                                               Default is value of $labels['name'].
 *     @type string[]     $labels                An array of labels for this post type. If not set, post
 *                                               labels are inherited for non-hierarchical types and page
 *                                               labels for hierarchical ones. See get_post_type_labels() for a full
 *                                               list of supported labels.
 *     @type string       $description           A short descriptive summary of what the post type is.
 *                                               Default empty.
 *     @type bool         $public                Whether a post type is intended for use publicly either via
 *                                               the admin interface or by front-end users. While the default
 *                                               settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                               and $show_in_nav_menus are inherited from $public, each does not
 *                                               rely on this relationship and controls a very specific intention.
 *                                               Default false.
 *     @type bool         $hierarchical          Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool         $exclude_from_search   Whether to exclude posts with this post type from front end search
 *                                               results. Default is the opposite value of $public.
 *     @type bool         $publicly_queryable    Whether queries can be performed on the front end for the post type
 *                                               as part of parse_request(). Endpoints would include:
 *                                               * ?post_type={post_type_key}
 *                                               * ?{post_type_key}={single_post_slug}
 *                                               * ?{post_type_query_var}={single_post_slug}
 *                                               If not set, the default is inherited from $public.
 *     @type bool         $show_ui               Whether to generate and allow a UI for managing this post type in the
 *                                               admin. Default is value of $public.
 *     @type bool|string  $show_in_menu          Where to show the post type in the admin menu. To work, $show_ui
 *                                               must be true. If true, the post type is shown in its own top level
 *                                               menu. If false, no menu is shown. If a string of an existing top
 *                                               level menu ('tools.php' or 'edit.php?post_type=page', for example), the
 *                                               post type will be placed as a sub-menu of that.
 *                                               Default is value of $show_ui.
 *     @type bool         $show_in_nav_menus     Makes this post type available for selection in navigation menus.
 *                                               Default is value of $public.
 *     @type bool         $show_in_admin_bar     Makes this post type available via the admin bar. Default is value
 *                                               of $show_in_menu.
 *     @type bool         $show_in_rest          Whether to include the post type in the REST API. Set this to true
 *                                               for the post type to be available in the block editor.
 *     @type string       $rest_base             To change the base URL of REST API route. Default is $post_type.
 *     @type string       $rest_namespace        To change the namespace URL of REST API route. Default is wp/v2.
 *     @type string       $rest_controller_class REST API controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type int          $menu_position         The position in the menu order the post type should appear. To work,
 *                                               $show_in_menu must be true. Default null (at the bottom).
 *     @type string       $menu_icon             The URL to the icon to be used for this menu. Pass a base64-encoded
 *                                               SVG using a data URI, which will be colored to match the color scheme
 *                                               -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                               of a Dashicons helper class to use a font icon, e.g.
 *                                               'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                               so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string|array $capability_type       The string to use to build the read, edit, and delete capabilities.
 *                                               May be passed as an array to allow for alternative plurals when using
 *                                               this argument as a base to construct the capabilities, e.g.
 *                                               array('story', 'stories'). Default 'post'.
 *     @type string[]     $capabilities          Array of capabilities for this post type. $capability_type is used
 *                                               as a base to construct capabilities by default.
 *                                               See get_post_type_capabilities().
 *     @type bool         $map_meta_cap          Whether to use the internal default meta capability handling.
 *                                               Default false.
 *     @type array        $supports              Core feature(s) the post type supports. Serves as an alias for calling
 *                                               add_post_type_support() directly. Core features include 'title',
 *                                               'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                               'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                               Additionally, the 'revisions' feature dictates whether the post type
 *                                               will store revisions, and the 'comments' feature dictates whether the
 *                                               comments count will show on the edit screen. A feature can also be
 *                                               specified as an array of arguments to provide additional information
 *                                               about supporting that feature.
 *                                               Example: `array( 'my_feature', array( 'field' => 'value' ) )`.
 *                                               Default is an array containing 'title' and 'editor'.
 *     @type callable     $register_meta_box_cb  Provide a callback function that sets up the meta boxes for the
 *                                               edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                               callback. Default null.
 *     @type string[]     $taxonomies            An array of taxonomy identifiers that will be registered for the
 *                                               post type. Taxonomies can be registered later with register_taxonomy()
 *                                               or register_taxonomy_for_object_type().
 *                                               Default empty array.
 *     @type bool|string  $has_archive           Whether there should be post type archives, or if a string, the
 *                                               archive slug to use. Will generate the proper rewrite rules if
 *                                               $rewrite is enabled. Default false.
 *     @type bool|array   $rewrite               {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type int    $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool  $query_var             Sets the query_var key for this post type. Defaults to $post_type
 *                                               key. If false, a post type cannot be loaded at
 *                                               ?{query_var}={post_slug}. If specified as a string, the query
 *                                               ?{query_var_string}={post_slug} will be valid.
 *     @type bool         $can_export            Whether to allow this post type to be exported. Default true.
 *     @type bool         $delete_with_user      Whether to delete posts of this type when deleting a user.
 *                                               * If true, posts of this type belonging to the user will be moved
 *                                                 to Trash when the user is deleted.
 *                                               * If false, posts of this type belonging to the user will *not*
 *                                                 be trashed or deleted.
 *                                               * If not set (the default), posts are trashed if post type supports
 *                                                 the 'author' feature. Otherwise posts are not trashed or deleted.
 *                                               Default null.
 *     @type array        $template              Array of blocks to use as the default initial state for an editor
 *                                               session. Each item should be an array containing block name and
 *                                               optional attributes. Default empty array.
 *     @type string|false $template_lock         Whether the block template should be locked if $template is set.
 *                                               * If set to 'all', the user is unable to insert new blocks,
 *                                                 move existing blocks and delete blocks.
 *                                               * If set to 'insert', the user is able to move existing blocks
 *                                                 but is unable to insert new blocks and delete blocks.
 *                                               Default false.
 *     @type bool         $_builtin              FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                               "built-in" post_type. Default false.
 *     @type string       $_edit_link            FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                               this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object on success,
 *                               WP_Error object on failure.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name.
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a `WP_Post_Type` object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    /**
     * Fires after a specific post type is registered.
     *
     * The dynamic portion of the filter name, `$post_type`, refers to the post type key.
     *
     * Possible hook names include:
     *
     *  - `registered_post_type_post`
     *  - `registered_post_type_page`
     *
     * @since 6.0.0
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action("registered_post_type_{$post_type}", $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 5.9

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of `WP_Post_Type`.
 * @since 4.7.0 Introduced `show_in_rest`, `rest_base` and `rest_controller_class`
 *              arguments to register the post type in REST API.
 * @since 5.0.0 The `template` and `template_lock` arguments were added.
 * @since 5.3.0 The `supports` argument will now accept an array of arguments for a feature.
 * @since 5.9.0 The `rest_namespace` argument was added.
 *
 * @global array $wp_post_types List of post types.
 *
 * @param string       $post_type Post type key. Must not exceed 20 characters and may
 *                                only contain lowercase alphanumeric characters, dashes,
 *                                and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string       $label                 Name of the post type shown in the menu. Usually plural.
 *                                               Default is value of $labels['name'].
 *     @type string[]     $labels                An array of labels for this post type. If not set, post
 *                                               labels are inherited for non-hierarchical types and page
 *                                               labels for hierarchical ones. See get_post_type_labels() for a full
 *                                               list of supported labels.
 *     @type string       $description           A short descriptive summary of what the post type is.
 *                                               Default empty.
 *     @type bool         $public                Whether a post type is intended for use publicly either via
 *                                               the admin interface or by front-end users. While the default
 *                                               settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                               and $show_in_nav_menus are inherited from $public, each does not
 *                                               rely on this relationship and controls a very specific intention.
 *                                               Default false.
 *     @type bool         $hierarchical          Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool         $exclude_from_search   Whether to exclude posts with this post type from front end search
 *                                               results. Default is the opposite value of $public.
 *     @type bool         $publicly_queryable    Whether queries can be performed on the front end for the post type
 *                                               as part of parse_request(). Endpoints would include:
 *                                               * ?post_type={post_type_key}
 *                                               * ?{post_type_key}={single_post_slug}
 *                                               * ?{post_type_query_var}={single_post_slug}
 *                                               If not set, the default is inherited from $public.
 *     @type bool         $show_ui               Whether to generate and allow a UI for managing this post type in the
 *                                               admin. Default is value of $public.
 *     @type bool|string  $show_in_menu          Where to show the post type in the admin menu. To work, $show_ui
 *                                               must be true. If true, the post type is shown in its own top level
 *                                               menu. If false, no menu is shown. If a string of an existing top
 *                                               level menu ('tools.php' or 'edit.php?post_type=page', for example), the
 *                                               post type will be placed as a sub-menu of that.
 *                                               Default is value of $show_ui.
 *     @type bool         $show_in_nav_menus     Makes this post type available for selection in navigation menus.
 *                                               Default is value of $public.
 *     @type bool         $show_in_admin_bar     Makes this post type available via the admin bar. Default is value
 *                                               of $show_in_menu.
 *     @type bool         $show_in_rest          Whether to include the post type in the REST API. Set this to true
 *                                               for the post type to be available in the block editor.
 *     @type string       $rest_base             To change the base URL of REST API route. Default is $post_type.
 *     @type string       $rest_namespace        To change the namespace URL of REST API route. Default is wp/v2.
 *     @type string       $rest_controller_class REST API controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type int          $menu_position         The position in the menu order the post type should appear. To work,
 *                                               $show_in_menu must be true. Default null (at the bottom).
 *     @type string       $menu_icon             The URL to the icon to be used for this menu. Pass a base64-encoded
 *                                               SVG using a data URI, which will be colored to match the color scheme
 *                                               -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                               of a Dashicons helper class to use a font icon, e.g.
 *                                               'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                               so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string|array $capability_type       The string to use to build the read, edit, and delete capabilities.
 *                                               May be passed as an array to allow for alternative plurals when using
 *                                               this argument as a base to construct the capabilities, e.g.
 *                                               array('story', 'stories'). Default 'post'.
 *     @type string[]     $capabilities          Array of capabilities for this post type. $capability_type is used
 *                                               as a base to construct capabilities by default.
 *                                               See get_post_type_capabilities().
 *     @type bool         $map_meta_cap          Whether to use the internal default meta capability handling.
 *                                               Default false.
 *     @type array        $supports              Core feature(s) the post type supports. Serves as an alias for calling
 *                                               add_post_type_support() directly. Core features include 'title',
 *                                               'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                               'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                               Additionally, the 'revisions' feature dictates whether the post type
 *                                               will store revisions, and the 'comments' feature dictates whether the
 *                                               comments count will show on the edit screen. A feature can also be
 *                                               specified as an array of arguments to provide additional information
 *                                               about supporting that feature.
 *                                               Example: `array( 'my_feature', array( 'field' => 'value' ) )`.
 *                                               Default is an array containing 'title' and 'editor'.
 *     @type callable     $register_meta_box_cb  Provide a callback function that sets up the meta boxes for the
 *                                               edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                               callback. Default null.
 *     @type string[]     $taxonomies            An array of taxonomy identifiers that will be registered for the
 *                                               post type. Taxonomies can be registered later with register_taxonomy()
 *                                               or register_taxonomy_for_object_type().
 *                                               Default empty array.
 *     @type bool|string  $has_archive           Whether there should be post type archives, or if a string, the
 *                                               archive slug to use. Will generate the proper rewrite rules if
 *                                               $rewrite is enabled. Default false.
 *     @type bool|array   $rewrite               {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type int    $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool  $query_var             Sets the query_var key for this post type. Defaults to $post_type
 *                                               key. If false, a post type cannot be loaded at
 *                                               ?{query_var}={post_slug}. If specified as a string, the query
 *                                               ?{query_var_string}={post_slug} will be valid.
 *     @type bool         $can_export            Whether to allow this post type to be exported. Default true.
 *     @type bool         $delete_with_user      Whether to delete posts of this type when deleting a user.
 *                                               * If true, posts of this type belonging to the user will be moved
 *                                                 to Trash when the user is deleted.
 *                                               * If false, posts of this type belonging to the user will *not*
 *                                                 be trashed or deleted.
 *                                               * If not set (the default), posts are trashed if post type supports
 *                                                 the 'author' feature. Otherwise posts are not trashed or deleted.
 *                                               Default null.
 *     @type array        $template              Array of blocks to use as the default initial state for an editor
 *                                               session. Each item should be an array containing block name and
 *                                               optional attributes. Default empty array.
 *     @type string|false $template_lock         Whether the block template should be locked if $template is set.
 *                                               * If set to 'all', the user is unable to insert new blocks,
 *                                                 move existing blocks and delete blocks.
 *                                               * If set to 'insert', the user is able to move existing blocks
 *                                                 but is unable to insert new blocks and delete blocks.
 *                                               Default false.
 *     @type bool         $_builtin              FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                               "built-in" post_type. Default false.
 *     @type string       $_edit_link            FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                               this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object on success,
 *                               WP_Error object on failure.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name.
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a `WP_Post_Type` object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 5.8

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of `WP_Post_Type`.
 * @since 4.7.0 Introduced `show_in_rest`, `rest_base` and `rest_controller_class`
 *              arguments to register the post type in REST API.
 * @since 5.0.0 The `template` and `template_lock` arguments were added.
 * @since 5.3.0 The `supports` argument will now accept an array of arguments for a feature.
 *
 * @global array $wp_post_types List of post types.
 *
 * @param string       $post_type Post type key. Must not exceed 20 characters and may
 *                                only contain lowercase alphanumeric characters, dashes,
 *                                and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string       $label                 Name of the post type shown in the menu. Usually plural.
 *                                               Default is value of $labels['name'].
 *     @type string[]     $labels                An array of labels for this post type. If not set, post
 *                                               labels are inherited for non-hierarchical types and page
 *                                               labels for hierarchical ones. See get_post_type_labels() for a full
 *                                               list of supported labels.
 *     @type string       $description           A short descriptive summary of what the post type is.
 *                                               Default empty.
 *     @type bool         $public                Whether a post type is intended for use publicly either via
 *                                               the admin interface or by front-end users. While the default
 *                                               settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                               and $show_in_nav_menus are inherited from public, each does not
 *                                               rely on this relationship and controls a very specific intention.
 *                                               Default false.
 *     @type bool         $hierarchical          Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool         $exclude_from_search   Whether to exclude posts with this post type from front end search
 *                                               results. Default is the opposite value of $public.
 *     @type bool         $publicly_queryable    Whether queries can be performed on the front end for the post type
 *                                               as part of parse_request(). Endpoints would include:
 *                                               * ?post_type={post_type_key}
 *                                               * ?{post_type_key}={single_post_slug}
 *                                               * ?{post_type_query_var}={single_post_slug}
 *                                               If not set, the default is inherited from $public.
 *     @type bool         $show_ui               Whether to generate and allow a UI for managing this post type in the
 *                                               admin. Default is value of $public.
 *     @type bool|string  $show_in_menu          Where to show the post type in the admin menu. To work, $show_ui
 *                                               must be true. If true, the post type is shown in its own top level
 *                                               menu. If false, no menu is shown. If a string of an existing top
 *                                               level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                               type will be placed as a sub-menu of that.
 *                                               Default is value of $show_ui.
 *     @type bool         $show_in_nav_menus     Makes this post type available for selection in navigation menus.
 *                                               Default is value of $public.
 *     @type bool         $show_in_admin_bar     Makes this post type available via the admin bar. Default is value
 *                                               of $show_in_menu.
 *     @type bool         $show_in_rest          Whether to include the post type in the REST API. Set this to true
 *                                               for the post type to be available in the block editor.
 *     @type string       $rest_base             To change the base url of REST API route. Default is $post_type.
 *     @type string       $rest_controller_class REST API Controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type int          $menu_position         The position in the menu order the post type should appear. To work,
 *                                               $show_in_menu must be true. Default null (at the bottom).
 *     @type string       $menu_icon             The url to the icon to be used for this menu. Pass a base64-encoded
 *                                               SVG using a data URI, which will be colored to match the color scheme
 *                                               -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                               of a Dashicons helper class to use a font icon, e.g.
 *                                               'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                               so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string       $capability_type       The string to use to build the read, edit, and delete capabilities.
 *                                               May be passed as an array to allow for alternative plurals when using
 *                                               this argument as a base to construct the capabilities, e.g.
 *                                               array('story', 'stories'). Default 'post'.
 *     @type string[]     $capabilities          Array of capabilities for this post type. $capability_type is used
 *                                               as a base to construct capabilities by default.
 *                                               See get_post_type_capabilities().
 *     @type bool         $map_meta_cap          Whether to use the internal default meta capability handling.
 *                                               Default false.
 *     @type array        $supports              Core feature(s) the post type supports. Serves as an alias for calling
 *                                               add_post_type_support() directly. Core features include 'title',
 *                                               'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                               'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                               Additionally, the 'revisions' feature dictates whether the post type
 *                                               will store revisions, and the 'comments' feature dictates whether the
 *                                               comments count will show on the edit screen. A feature can also be
 *                                               specified as an array of arguments to provide additional information
 *                                               about supporting that feature.
 *                                               Example: `array( 'my_feature', array( 'field' => 'value' ) )`.
 *                                               Default is an array containing 'title' and 'editor'.
 *     @type callable     $register_meta_box_cb  Provide a callback function that sets up the meta boxes for the
 *                                               edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                               callback. Default null.
 *     @type string[]     $taxonomies            An array of taxonomy identifiers that will be registered for the
 *                                               post type. Taxonomies can be registered later with register_taxonomy()
 *                                               or register_taxonomy_for_object_type().
 *                                               Default empty array.
 *     @type bool|string  $has_archive           Whether there should be post type archives, or if a string, the
 *                                               archive slug to use. Will generate the proper rewrite rules if
 *                                               $rewrite is enabled. Default false.
 *     @type bool|array   $rewrite               {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type int    $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool  $query_var             Sets the query_var key for this post type. Defaults to $post_type
 *                                               key. If false, a post type cannot be loaded at
 *                                               ?{query_var}={post_slug}. If specified as a string, the query
 *                                               ?{query_var_string}={post_slug} will be valid.
 *     @type bool         $can_export            Whether to allow this post type to be exported. Default true.
 *     @type bool         $delete_with_user      Whether to delete posts of this type when deleting a user.
 *                                               * If true, posts of this type belonging to the user will be moved
 *                                                 to Trash when the user is deleted.
 *                                               * If false, posts of this type belonging to the user will *not*
 *                                                 be trashed or deleted.
 *                                               * If not set (the default), posts are trashed if post type supports
 *                                                 the 'author' feature. Otherwise posts are not trashed or deleted.
 *                                               Default null.
 *     @type array        $template              Array of blocks to use as the default initial state for an editor
 *                                               session. Each item should be an array containing block name and
 *                                               optional attributes. Default empty array.
 *     @type string|false $template_lock         Whether the block template should be locked if $template is set.
 *                                               * If set to 'all', the user is unable to insert new blocks,
 *                                                 move existing blocks and delete blocks.
 *                                               * If set to 'insert', the user is able to move existing blocks
 *                                                 but is unable to insert new blocks and delete blocks.
 *                                               Default false.
 *     @type bool         $_builtin              FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                               "built-in" post_type. Default false.
 *     @type string       $_edit_link            FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                               this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object on success,
 *                               WP_Error object on failure.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name.
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a `WP_Post_Type` object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 5.7

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of `WP_Post_Type`.
 * @since 4.7.0 Introduced `show_in_rest`, `rest_base` and `rest_controller_class`
 *              arguments to register the post type in REST API.
 * @since 5.0.0 The `template` and `template_lock` arguments were added.
 * @since 5.3.0 The `supports` argument will now accept an array of arguments for a feature.
 *
 * @global array $wp_post_types List of post types.
 *
 * @param string       $post_type Post type key. Must not exceed 20 characters and may
 *                                only contain lowercase alphanumeric characters, dashes,
 *                                and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string       $label                 Name of the post type shown in the menu. Usually plural.
 *                                               Default is value of $labels['name'].
 *     @type string[]     $labels                An array of labels for this post type. If not set, post
 *                                               labels are inherited for non-hierarchical types and page
 *                                               labels for hierarchical ones. See get_post_type_labels() for a full
 *                                               list of supported labels.
 *     @type string       $description           A short descriptive summary of what the post type is.
 *                                               Default empty.
 *     @type bool         $public                Whether a post type is intended for use publicly either via
 *                                               the admin interface or by front-end users. While the default
 *                                               settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                               and $show_in_nav_menus are inherited from public, each does not
 *                                               rely on this relationship and controls a very specific intention.
 *                                               Default false.
 *     @type bool         $hierarchical          Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool         $exclude_from_search   Whether to exclude posts with this post type from front end search
 *                                               results. Default is the opposite value of $public.
 *     @type bool         $publicly_queryable    Whether queries can be performed on the front end for the post type
 *                                               as part of parse_request(). Endpoints would include:
 *                                               * ?post_type={post_type_key}
 *                                               * ?{post_type_key}={single_post_slug}
 *                                               * ?{post_type_query_var}={single_post_slug}
 *                                               If not set, the default is inherited from $public.
 *     @type bool         $show_ui               Whether to generate and allow a UI for managing this post type in the
 *                                               admin. Default is value of $public.
 *     @type bool|string  $show_in_menu          Where to show the post type in the admin menu. To work, $show_ui
 *                                               must be true. If true, the post type is shown in its own top level
 *                                               menu. If false, no menu is shown. If a string of an existing top
 *                                               level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                               type will be placed as a sub-menu of that.
 *                                               Default is value of $show_ui.
 *     @type bool         $show_in_nav_menus     Makes this post type available for selection in navigation menus.
 *                                               Default is value of $public.
 *     @type bool         $show_in_admin_bar     Makes this post type available via the admin bar. Default is value
 *                                               of $show_in_menu.
 *     @type bool         $show_in_rest          Whether to include the post type in the REST API. Set this to true
 *                                               for the post type to be available in the block editor.
 *     @type string       $rest_base             To change the base url of REST API route. Default is $post_type.
 *     @type string       $rest_controller_class REST API Controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type int          $menu_position         The position in the menu order the post type should appear. To work,
 *                                               $show_in_menu must be true. Default null (at the bottom).
 *     @type string       $menu_icon             The url to the icon to be used for this menu. Pass a base64-encoded
 *                                               SVG using a data URI, which will be colored to match the color scheme
 *                                               -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                               of a Dashicons helper class to use a font icon, e.g.
 *                                               'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                               so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string       $capability_type       The string to use to build the read, edit, and delete capabilities.
 *                                               May be passed as an array to allow for alternative plurals when using
 *                                               this argument as a base to construct the capabilities, e.g.
 *                                               array('story', 'stories'). Default 'post'.
 *     @type string[]     $capabilities          Array of capabilities for this post type. $capability_type is used
 *                                               as a base to construct capabilities by default.
 *                                               See get_post_type_capabilities().
 *     @type bool         $map_meta_cap          Whether to use the internal default meta capability handling.
 *                                               Default false.
 *     @type array        $supports              Core feature(s) the post type supports. Serves as an alias for calling
 *                                               add_post_type_support() directly. Core features include 'title',
 *                                               'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                               'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                               Additionally, the 'revisions' feature dictates whether the post type
 *                                               will store revisions, and the 'comments' feature dictates whether the
 *                                               comments count will show on the edit screen. A feature can also be
 *                                               specified as an array of arguments to provide additional information
 *                                               about supporting that feature.
 *                                               Example: `array( 'my_feature', array( 'field' => 'value' ) )`.
 *                                               Default is an array containing 'title' and 'editor'.
 *     @type callable     $register_meta_box_cb  Provide a callback function that sets up the meta boxes for the
 *                                               edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                               callback. Default null.
 *     @type string[]     $taxonomies            An array of taxonomy identifiers that will be registered for the
 *                                               post type. Taxonomies can be registered later with register_taxonomy()
 *                                               or register_taxonomy_for_object_type().
 *                                               Default empty array.
 *     @type bool|string  $has_archive           Whether there should be post type archives, or if a string, the
 *                                               archive slug to use. Will generate the proper rewrite rules if
 *                                               $rewrite is enabled. Default false.
 *     @type bool|array   $rewrite               {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type int    $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool  $query_var             Sets the query_var key for this post type. Defaults to $post_type
 *                                               key. If false, a post type cannot be loaded at
 *                                               ?{query_var}={post_slug}. If specified as a string, the query
 *                                               ?{query_var_string}={post_slug} will be valid.
 *     @type bool         $can_export            Whether to allow this post type to be exported. Default true.
 *     @type bool         $delete_with_user      Whether to delete posts of this type when deleting a user.
 *                                               - If true, posts of this type belonging to the user will be moved
 *                                                 to Trash when the user is deleted.
 *                                               - If false, posts of this type belonging to the user will *not*
 *                                                 be trashed or deleted.
 *                                               - If not set (the default), posts are trashed if post type supports
 *                                                 the 'author' feature. Otherwise posts are not trashed or deleted.
 *                                               Default null.
 *     @type array        $template              Array of blocks to use as the default initial state for an editor
 *                                               session. Each item should be an array containing block name and
 *                                               optional attributes. Default empty array.
 *     @type string|false $template_lock         Whether the block template should be locked if $template is set.
 *                                               - If set to 'all', the user is unable to insert new blocks,
 *                                                 move existing blocks and delete blocks.
 *                                               - If set to 'insert', the user is able to move existing blocks
 *                                                 but is unable to insert new blocks and delete blocks.
 *                                               Default false.
 *     @type bool         $_builtin              FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                               "built-in" post_type. Default false.
 *     @type string       $_edit_link            FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                               this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object on success,
 *                               WP_Error object on failure.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name.
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a `WP_Post_Type` object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 5.6

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of `WP_Post_Type`.
 * @since 4.7.0 Introduced `show_in_rest`, `rest_base` and `rest_controller_class`
 *              arguments to register the post type in REST API.
 * @since 5.0.0 The `template` and `template_lock` arguments were added.
 * @since 5.3.0 The `supports` argument will now accept an array of arguments for a feature.
 *
 * @global array $wp_post_types List of post types.
 *
 * @param string       $post_type Post type key. Must not exceed 20 characters and may
 *                                only contain lowercase alphanumeric characters, dashes,
 *                                and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string       $label                 Name of the post type shown in the menu. Usually plural.
 *                                               Default is value of $labels['name'].
 *     @type array        $labels                An array of labels for this post type. If not set, post
 *                                               labels are inherited for non-hierarchical types and page
 *                                               labels for hierarchical ones. See get_post_type_labels() for a full
 *                                               list of supported labels.
 *     @type string       $description           A short descriptive summary of what the post type is.
 *                                               Default empty.
 *     @type bool         $public                Whether a post type is intended for use publicly either via
 *                                               the admin interface or by front-end users. While the default
 *                                               settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                               and $show_in_nav_menus are inherited from public, each does not
 *                                               rely on this relationship and controls a very specific intention.
 *                                               Default false.
 *     @type bool         $hierarchical          Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool         $exclude_from_search   Whether to exclude posts with this post type from front end search
 *                                               results. Default is the opposite value of $public.
 *     @type bool         $publicly_queryable    Whether queries can be performed on the front end for the post type
 *                                               as part of parse_request(). Endpoints would include:
 *                                               * ?post_type={post_type_key}
 *                                               * ?{post_type_key}={single_post_slug}
 *                                               * ?{post_type_query_var}={single_post_slug}
 *                                               If not set, the default is inherited from $public.
 *     @type bool         $show_ui               Whether to generate and allow a UI for managing this post type in the
 *                                               admin. Default is value of $public.
 *     @type bool|string  $show_in_menu          Where to show the post type in the admin menu. To work, $show_ui
 *                                               must be true. If true, the post type is shown in its own top level
 *                                               menu. If false, no menu is shown. If a string of an existing top
 *                                               level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                               type will be placed as a sub-menu of that.
 *                                               Default is value of $show_ui.
 *     @type bool         $show_in_nav_menus     Makes this post type available for selection in navigation menus.
 *                                               Default is value of $public.
 *     @type bool         $show_in_admin_bar     Makes this post type available via the admin bar. Default is value
 *                                               of $show_in_menu.
 *     @type bool         $show_in_rest          Whether to include the post type in the REST API. Set this to true
 *                                               for the post type to be available in the block editor.
 *     @type string       $rest_base             To change the base url of REST API route. Default is $post_type.
 *     @type string       $rest_controller_class REST API Controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type int          $menu_position         The position in the menu order the post type should appear. To work,
 *                                               $show_in_menu must be true. Default null (at the bottom).
 *     @type string       $menu_icon             The url to the icon to be used for this menu. Pass a base64-encoded
 *                                               SVG using a data URI, which will be colored to match the color scheme
 *                                               -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                               of a Dashicons helper class to use a font icon, e.g.
 *                                               'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                               so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string       $capability_type       The string to use to build the read, edit, and delete capabilities.
 *                                               May be passed as an array to allow for alternative plurals when using
 *                                               this argument as a base to construct the capabilities, e.g.
 *                                               array('story', 'stories'). Default 'post'.
 *     @type array        $capabilities          Array of capabilities for this post type. $capability_type is used
 *                                               as a base to construct capabilities by default.
 *                                               See get_post_type_capabilities().
 *     @type bool         $map_meta_cap          Whether to use the internal default meta capability handling.
 *                                               Default false.
 *     @type array        $supports              Core feature(s) the post type supports. Serves as an alias for calling
 *                                               add_post_type_support() directly. Core features include 'title',
 *                                               'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                               'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                               Additionally, the 'revisions' feature dictates whether the post type
 *                                               will store revisions, and the 'comments' feature dictates whether the
 *                                               comments count will show on the edit screen. A feature can also be
 *                                               specified as an array of arguments to provide additional information
 *                                               about supporting that feature.
 *                                               Example: `array( 'my_feature', array( 'field' => 'value' ) )`.
 *                                               Default is an array containing 'title' and 'editor'.
 *     @type callable     $register_meta_box_cb  Provide a callback function that sets up the meta boxes for the
 *                                               edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                               callback. Default null.
 *     @type array        $taxonomies            An array of taxonomy identifiers that will be registered for the
 *                                               post type. Taxonomies can be registered later with register_taxonomy()
 *                                               or register_taxonomy_for_object_type().
 *                                               Default empty array.
 *     @type bool|string  $has_archive           Whether there should be post type archives, or if a string, the
 *                                               archive slug to use. Will generate the proper rewrite rules if
 *                                               $rewrite is enabled. Default false.
 *     @type bool|array   $rewrite               {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type const  $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool  $query_var             Sets the query_var key for this post type. Defaults to $post_type
 *                                               key. If false, a post type cannot be loaded at
 *                                               ?{query_var}={post_slug}. If specified as a string, the query
 *                                               ?{query_var_string}={post_slug} will be valid.
 *     @type bool         $can_export            Whether to allow this post type to be exported. Default true.
 *     @type bool         $delete_with_user      Whether to delete posts of this type when deleting a user.
 *                                               - If true, posts of this type belonging to the user will be moved
 *                                                 to Trash when the user is deleted.
 *                                               - If false, posts of this type belonging to the user will *not*
 *                                                 be trashed or deleted.
 *                                               - If not set (the default), posts are trashed if post type supports
 *                                                 the 'author' feature. Otherwise posts are not trashed or deleted.
 *                                               Default null.
 *     @type array        $template              Array of blocks to use as the default initial state for an editor
 *                                               session. Each item should be an array containing block name and
 *                                               optional attributes. Default empty array.
 *     @type string|false $template_lock         Whether the block template should be locked if $template is set.
 *                                               - If set to 'all', the user is unable to insert new blocks,
 *                                                 move existing blocks and delete blocks.
 *                                               - If set to 'insert', the user is able to move existing blocks
 *                                                 but is unable to insert new blocks and delete blocks.
 *                                               Default false.
 *     @type bool         $_builtin              FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                               "built-in" post_type. Default false.
 *     @type string       $_edit_link            FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                               this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object on success,
 *                               WP_Error object on failure.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name.
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a `WP_Post_Type` object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 5.5

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of `WP_Post_Type`.
 * @since 4.7.0 Introduced `show_in_rest`, `rest_base` and `rest_controller_class`
 *              arguments to register the post type in REST API.
 * @since 5.3.0 The `supports` argument will now accept an array of arguments for a feature.
 * .
 * @global array $wp_post_types List of post types.
 *
 * @param string       $post_type Post type key. Must not exceed 20 characters and may
 *                                only contain lowercase alphanumeric characters, dashes,
 *                                and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string      $label                 Name of the post type shown in the menu. Usually plural.
 *                                              Default is value of $labels['name'].
 *     @type array       $labels                An array of labels for this post type. If not set, post
 *                                              labels are inherited for non-hierarchical types and page
 *                                              labels for hierarchical ones. See get_post_type_labels() for a full
 *                                              list of supported labels.
 *     @type string      $description           A short descriptive summary of what the post type is.
 *                                              Default empty.
 *     @type bool        $public                Whether a post type is intended for use publicly either via
 *                                              the admin interface or by front-end users. While the default
 *                                              settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                              and $show_in_nav_menus are inherited from public, each does not
 *                                              rely on this relationship and controls a very specific intention.
 *                                              Default false.
 *     @type bool        $hierarchical          Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool        $exclude_from_search   Whether to exclude posts with this post type from front end search
 *                                              results. Default is the opposite value of $public.
 *     @type bool        $publicly_queryable    Whether queries can be performed on the front end for the post type
 *                                              as part of parse_request(). Endpoints would include:
 *                                              * ?post_type={post_type_key}
 *                                              * ?{post_type_key}={single_post_slug}
 *                                              * ?{post_type_query_var}={single_post_slug}
 *                                              If not set, the default is inherited from $public.
 *     @type bool        $show_ui               Whether to generate and allow a UI for managing this post type in the
 *                                              admin. Default is value of $public.
 *     @type bool|string $show_in_menu          Where to show the post type in the admin menu. To work, $show_ui
 *                                              must be true. If true, the post type is shown in its own top level
 *                                              menu. If false, no menu is shown. If a string of an existing top
 *                                              level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                              type will be placed as a sub-menu of that.
 *                                              Default is value of $show_ui.
 *     @type bool        $show_in_nav_menus     Makes this post type available for selection in navigation menus.
 *                                              Default is value of $public.
 *     @type bool        $show_in_admin_bar     Makes this post type available via the admin bar. Default is value
 *                                              of $show_in_menu.
 *     @type bool        $show_in_rest          Whether to include the post type in the REST API. Set this to true
 *                                              for the post type to be available in the block editor.
 *     @type string      $rest_base             To change the base url of REST API route. Default is $post_type.
 *     @type string      $rest_controller_class REST API Controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type int         $menu_position         The position in the menu order the post type should appear. To work,
 *                                              $show_in_menu must be true. Default null (at the bottom).
 *     @type string      $menu_icon             The url to the icon to be used for this menu. Pass a base64-encoded
 *                                              SVG using a data URI, which will be colored to match the color scheme
 *                                              -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                              of a Dashicons helper class to use a font icon, e.g.
 *                                              'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                              so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string      $capability_type       The string to use to build the read, edit, and delete capabilities.
 *                                              May be passed as an array to allow for alternative plurals when using
 *                                              this argument as a base to construct the capabilities, e.g.
 *                                              array('story', 'stories'). Default 'post'.
 *     @type array       $capabilities          Array of capabilities for this post type. $capability_type is used
 *                                              as a base to construct capabilities by default.
 *                                              See get_post_type_capabilities().
 *     @type bool        $map_meta_cap          Whether to use the internal default meta capability handling.
 *                                              Default false.
 *     @type array       $supports              Core feature(s) the post type supports. Serves as an alias for calling
 *                                              add_post_type_support() directly. Core features include 'title',
 *                                              'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                              'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                              Additionally, the 'revisions' feature dictates whether the post type
 *                                              will store revisions, and the 'comments' feature dictates whether the
 *                                              comments count will show on the edit screen. A feature can also be
 *                                              specified as an array of arguments to provide additional information
 *                                              about supporting that feature.
 *                                              Example: `array( 'my_feature', array( 'field' => 'value' ) )`.
 *                                              Default is an array containing 'title' and 'editor'.
 *     @type callable    $register_meta_box_cb  Provide a callback function that sets up the meta boxes for the
 *                                              edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                              callback. Default null.
 *     @type array       $taxonomies            An array of taxonomy identifiers that will be registered for the
 *                                              post type. Taxonomies can be registered later with register_taxonomy()
 *                                              or register_taxonomy_for_object_type().
 *                                              Default empty array.
 *     @type bool|string $has_archive           Whether there should be post type archives, or if a string, the
 *                                              archive slug to use. Will generate the proper rewrite rules if
 *                                              $rewrite is enabled. Default false.
 *     @type bool|array  $rewrite              {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type const  $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool $query_var             Sets the query_var key for this post type. Defaults to $post_type
 *                                              key. If false, a post type cannot be loaded at
 *                                              ?{query_var}={post_slug}. If specified as a string, the query
 *                                              ?{query_var_string}={post_slug} will be valid.
 *     @type bool        $can_export            Whether to allow this post type to be exported. Default true.
 *     @type bool        $delete_with_user      Whether to delete posts of this type when deleting a user. If true,
 *                                              posts of this type belonging to the user will be moved to Trash
 *                                              when then user is deleted. If false, posts of this type belonging
 *                                              to the user will *not* be trashed or deleted. If not set (the default),
 *                                              posts are trashed if post_type_supports('author'). Otherwise posts
 *                                              are not trashed or deleted. Default null.
 *     @type bool        $_builtin              FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                              "built-in" post_type. Default false.
 *     @type string      $_edit_link            FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                              this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object on success,
 *                               WP_Error object on failure.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name.
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a `WP_Post_Type` object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 5.4

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of `WP_Post_Type`.
 * @since 4.7.0 Introduced `show_in_rest`, `rest_base` and `rest_controller_class`
 *              arguments to register the post type in REST API.
 * @since 5.3.0 The `supports` argument will now accept an array of arguments for a feature.
 * .
 * @global array $wp_post_types List of post types.
 *
 * @param string $post_type Post type key. Must not exceed 20 characters and may
 *                          only contain lowercase alphanumeric characters, dashes,
 *                          and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string      $label                 Name of the post type shown in the menu. Usually plural.
 *                                              Default is value of $labels['name'].
 *     @type array       $labels                An array of labels for this post type. If not set, post
 *                                              labels are inherited for non-hierarchical types and page
 *                                              labels for hierarchical ones. See get_post_type_labels() for a full
 *                                              list of supported labels.
 *     @type string      $description           A short descriptive summary of what the post type is.
 *                                              Default empty.
 *     @type bool        $public                Whether a post type is intended for use publicly either via
 *                                              the admin interface or by front-end users. While the default
 *                                              settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                              and $show_in_nav_menus are inherited from public, each does not
 *                                              rely on this relationship and controls a very specific intention.
 *                                              Default false.
 *     @type bool        $hierarchical          Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool        $exclude_from_search   Whether to exclude posts with this post type from front end search
 *                                              results. Default is the opposite value of $public.
 *     @type bool        $publicly_queryable    Whether queries can be performed on the front end for the post type
 *                                              as part of parse_request(). Endpoints would include:
 *                                              * ?post_type={post_type_key}
 *                                              * ?{post_type_key}={single_post_slug}
 *                                              * ?{post_type_query_var}={single_post_slug}
 *                                              If not set, the default is inherited from $public.
 *     @type bool        $show_ui               Whether to generate and allow a UI for managing this post type in the
 *                                              admin. Default is value of $public.
 *     @type bool|string $show_in_menu          Where to show the post type in the admin menu. To work, $show_ui
 *                                              must be true. If true, the post type is shown in its own top level
 *                                              menu. If false, no menu is shown. If a string of an existing top
 *                                              level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                              type will be placed as a sub-menu of that.
 *                                              Default is value of $show_ui.
 *     @type bool        $show_in_nav_menus     Makes this post type available for selection in navigation menus.
 *                                              Default is value of $public.
 *     @type bool        $show_in_admin_bar     Makes this post type available via the admin bar. Default is value
 *                                              of $show_in_menu.
 *     @type bool        $show_in_rest          Whether to include the post type in the REST API. Set this to true
 *                                              for the post type to be available in the block editor.
 *     @type string      $rest_base             To change the base url of REST API route. Default is $post_type.
 *     @type string      $rest_controller_class REST API Controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type int         $menu_position         The position in the menu order the post type should appear. To work,
 *                                              $show_in_menu must be true. Default null (at the bottom).
 *     @type string      $menu_icon             The url to the icon to be used for this menu. Pass a base64-encoded
 *                                              SVG using a data URI, which will be colored to match the color scheme
 *                                              -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                              of a Dashicons helper class to use a font icon, e.g.
 *                                              'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                              so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string      $capability_type       The string to use to build the read, edit, and delete capabilities.
 *                                              May be passed as an array to allow for alternative plurals when using
 *                                              this argument as a base to construct the capabilities, e.g.
 *                                              array('story', 'stories'). Default 'post'.
 *     @type array       $capabilities          Array of capabilities for this post type. $capability_type is used
 *                                              as a base to construct capabilities by default.
 *                                              See get_post_type_capabilities().
 *     @type bool        $map_meta_cap          Whether to use the internal default meta capability handling.
 *                                              Default false.
 *     @type array       $supports              Core feature(s) the post type supports. Serves as an alias for calling
 *                                              add_post_type_support() directly. Core features include 'title',
 *                                              'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                              'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                              Additionally, the 'revisions' feature dictates whether the post type
 *                                              will store revisions, and the 'comments' feature dictates whether the
 *                                              comments count will show on the edit screen. A feature can also be
 *                                              specified as an array of arguments to provide additional information
 *                                              about supporting that feature. Example: `array( 'my_feature', array(
 *                                              'field' => 'value' ) )`. Default is an array containing 'title' and
 *                                              'editor'.
 *     @type callable    $register_meta_box_cb  Provide a callback function that sets up the meta boxes for the
 *                                              edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                              callback. Default null.
 *     @type array       $taxonomies            An array of taxonomy identifiers that will be registered for the
 *                                              post type. Taxonomies can be registered later with register_taxonomy()
 *                                              or register_taxonomy_for_object_type().
 *                                              Default empty array.
 *     @type bool|string $has_archive           Whether there should be post type archives, or if a string, the
 *                                              archive slug to use. Will generate the proper rewrite rules if
 *                                              $rewrite is enabled. Default false.
 *     @type bool|array  $rewrite              {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type const  $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool $query_var             Sets the query_var key for this post type. Defaults to $post_type
 *                                              key. If false, a post type cannot be loaded at
 *                                              ?{query_var}={post_slug}. If specified as a string, the query
 *                                              ?{query_var_string}={post_slug} will be valid.
 *     @type bool        $can_export            Whether to allow this post type to be exported. Default true.
 *     @type bool        $delete_with_user      Whether to delete posts of this type when deleting a user. If true,
 *                                              posts of this type belonging to the user will be moved to Trash
 *                                              when then user is deleted. If false, posts of this type belonging
 *                                              to the user will *not* be trashed or deleted. If not set (the default),
 *                                              posts are trashed if post_type_supports('author'). Otherwise posts
 *                                              are not trashed or deleted. Default null.
 *     @type bool        $_builtin              FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                              "built-in" post_type. Default false.
 *     @type string      $_edit_link            FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                              this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object on success,
 *                               WP_Error object on failure.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name.
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a `WP_Post_Type` object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 5.3

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of `WP_Post_Type`.
 * @since 4.7.0 Introduced `show_in_rest`, `rest_base` and `rest_controller_class`
 *              arguments to register the post type in REST API.
 * @since 5.3.0 The `supports` argument will now accept an array of arguments for a feature.
 * .
 * @global array $wp_post_types List of post types.
 *
 * @param string $post_type Post type key. Must not exceed 20 characters and may
 *                          only contain lowercase alphanumeric characters, dashes,
 *                          and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string      $label                 Name of the post type shown in the menu. Usually plural.
 *                                              Default is value of $labels['name'].
 *     @type array       $labels                An array of labels for this post type. If not set, post
 *                                              labels are inherited for non-hierarchical types and page
 *                                              labels for hierarchical ones. See get_post_type_labels() for a full
 *                                              list of supported labels.
 *     @type string      $description           A short descriptive summary of what the post type is.
 *                                              Default empty.
 *     @type bool        $public                Whether a post type is intended for use publicly either via
 *                                              the admin interface or by front-end users. While the default
 *                                              settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                              and $show_in_nav_menus are inherited from public, each does not
 *                                              rely on this relationship and controls a very specific intention.
 *                                              Default false.
 *     @type bool        $hierarchical          Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool        $exclude_from_search   Whether to exclude posts with this post type from front end search
 *                                              results. Default is the opposite value of $public.
 *     @type bool        $publicly_queryable    Whether queries can be performed on the front end for the post type
 *                                              as part of parse_request(). Endpoints would include:
 *                                              * ?post_type={post_type_key}
 *                                              * ?{post_type_key}={single_post_slug}
 *                                              * ?{post_type_query_var}={single_post_slug}
 *                                              If not set, the default is inherited from $public.
 *     @type bool        $show_ui               Whether to generate and allow a UI for managing this post type in the
 *                                              admin. Default is value of $public.
 *     @type bool|string $show_in_menu          Where to show the post type in the admin menu. To work, $show_ui
 *                                              must be true. If true, the post type is shown in its own top level
 *                                              menu. If false, no menu is shown. If a string of an existing top
 *                                              level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                              type will be placed as a sub-menu of that.
 *                                              Default is value of $show_ui.
 *     @type bool        $show_in_nav_menus     Makes this post type available for selection in navigation menus.
 *                                              Default is value of $public.
 *     @type bool        $show_in_admin_bar     Makes this post type available via the admin bar. Default is value
 *                                              of $show_in_menu.
 *     @type bool        $show_in_rest          Whether to include the post type in the REST API. Set this to true
 *                                              for the post type to be available in the block editor.
 *     @type string      $rest_base             To change the base url of REST API route. Default is $post_type.
 *     @type string      $rest_controller_class REST API Controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type int         $menu_position         The position in the menu order the post type should appear. To work,
 *                                              $show_in_menu must be true. Default null (at the bottom).
 *     @type string      $menu_icon             The url to the icon to be used for this menu. Pass a base64-encoded
 *                                              SVG using a data URI, which will be colored to match the color scheme
 *                                              -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                              of a Dashicons helper class to use a font icon, e.g.
 *                                              'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                              so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string      $capability_type       The string to use to build the read, edit, and delete capabilities.
 *                                              May be passed as an array to allow for alternative plurals when using
 *                                              this argument as a base to construct the capabilities, e.g.
 *                                              array('story', 'stories'). Default 'post'.
 *     @type array       $capabilities          Array of capabilities for this post type. $capability_type is used
 *                                              as a base to construct capabilities by default.
 *                                              See get_post_type_capabilities().
 *     @type bool        $map_meta_cap          Whether to use the internal default meta capability handling.
 *                                              Default false.
 *     @type array       $supports              Core feature(s) the post type supports. Serves as an alias for calling
 *                                              add_post_type_support() directly. Core features include 'title',
 *                                              'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                              'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                              Additionally, the 'revisions' feature dictates whether the post type
 *                                              will store revisions, and the 'comments' feature dictates whether the
 *                                              comments count will show on the edit screen. A feature can also be
 *                                              specified as an array of arguments to provide additional information
 *                                              about supporting that feature. Example: `array( 'my_feature', array(
 *                                              'field' => 'value' ) )`. Default is an array containing 'title' and
 *                                              'editor'.
 *     @type callable    $register_meta_box_cb  Provide a callback function that sets up the meta boxes for the
 *                                              edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                              callback. Default null.
 *     @type array       $taxonomies            An array of taxonomy identifiers that will be registered for the
 *                                              post type. Taxonomies can be registered later with register_taxonomy()
 *                                              or register_taxonomy_for_object_type().
 *                                              Default empty array.
 *     @type bool|string $has_archive           Whether there should be post type archives, or if a string, the
 *                                              archive slug to use. Will generate the proper rewrite rules if
 *                                              $rewrite is enabled. Default false.
 *     @type bool|array  $rewrite              {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type const  $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool $query_var             Sets the query_var key for this post type. Defaults to $post_type
 *                                              key. If false, a post type cannot be loaded at
 *                                              ?{query_var}={post_slug}. If specified as a string, the query
 *                                              ?{query_var_string}={post_slug} will be valid.
 *     @type bool        $can_export            Whether to allow this post type to be exported. Default true.
 *     @type bool        $delete_with_user      Whether to delete posts of this type when deleting a user. If true,
 *                                              posts of this type belonging to the user will be moved to trash
 *                                              when then user is deleted. If false, posts of this type belonging
 *                                              to the user will *not* be trashed or deleted. If not set (the default),
 *                                              posts are trashed if post_type_supports('author'). Otherwise posts
 *                                              are not trashed or deleted. Default null.
 *     @type bool        $_builtin              FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                              "built-in" post_type. Default false.
 *     @type string      $_edit_link            FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                              this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object, or an error object.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a `WP_Post_Type` object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 5.1

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of `WP_Post_Type`.
 * @since 4.7.0 Introduced `show_in_rest`, `rest_base` and `rest_controller_class`
 *              arguments to register the post type in REST API.
 *
 * @global array $wp_post_types List of post types.
 *
 * @param string $post_type Post type key. Must not exceed 20 characters and may
 *                          only contain lowercase alphanumeric characters, dashes,
 *                          and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string      $label                 Name of the post type shown in the menu. Usually plural.
 *                                              Default is value of $labels['name'].
 *     @type array       $labels                An array of labels for this post type. If not set, post
 *                                              labels are inherited for non-hierarchical types and page
 *                                              labels for hierarchical ones. See get_post_type_labels() for a full
 *                                              list of supported labels.
 *     @type string      $description           A short descriptive summary of what the post type is.
 *                                              Default empty.
 *     @type bool        $public                Whether a post type is intended for use publicly either via
 *                                              the admin interface or by front-end users. While the default
 *                                              settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                              and $show_in_nav_menus are inherited from public, each does not
 *                                              rely on this relationship and controls a very specific intention.
 *                                              Default false.
 *     @type bool        $hierarchical          Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool        $exclude_from_search   Whether to exclude posts with this post type from front end search
 *                                              results. Default is the opposite value of $public.
 *     @type bool        $publicly_queryable    Whether queries can be performed on the front end for the post type
 *                                              as part of parse_request(). Endpoints would include:
 *                                              * ?post_type={post_type_key}
 *                                              * ?{post_type_key}={single_post_slug}
 *                                              * ?{post_type_query_var}={single_post_slug}
 *                                              If not set, the default is inherited from $public.
 *     @type bool        $show_ui               Whether to generate and allow a UI for managing this post type in the
 *                                              admin. Default is value of $public.
 *     @type bool        $show_in_menu          Where to show the post type in the admin menu. To work, $show_ui
 *                                              must be true. If true, the post type is shown in its own top level
 *                                              menu. If false, no menu is shown. If a string of an existing top
 *                                              level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                              type will be placed as a sub-menu of that.
 *                                              Default is value of $show_ui.
 *     @type bool        $show_in_nav_menus     Makes this post type available for selection in navigation menus.
 *                                              Default is value $public.
 *     @type bool        $show_in_admin_bar     Makes this post type available via the admin bar. Default is value
 *                                              of $show_in_menu.
 *     @type bool        $show_in_rest          Whether to add the post type route in the REST API 'wp/v2' namespace.
 *     @type string      $rest_base             To change the base url of REST API route. Default is $post_type.
 *     @type string      $rest_controller_class REST API Controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type int         $menu_position         The position in the menu order the post type should appear. To work,
 *                                              $show_in_menu must be true. Default null (at the bottom).
 *     @type string      $menu_icon             The url to the icon to be used for this menu. Pass a base64-encoded
 *                                              SVG using a data URI, which will be colored to match the color scheme
 *                                              -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                              of a Dashicons helper class to use a font icon, e.g.
 *                                              'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                              so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string      $capability_type       The string to use to build the read, edit, and delete capabilities.
 *                                              May be passed as an array to allow for alternative plurals when using
 *                                              this argument as a base to construct the capabilities, e.g.
 *                                              array('story', 'stories'). Default 'post'.
 *     @type array       $capabilities          Array of capabilities for this post type. $capability_type is used
 *                                              as a base to construct capabilities by default.
 *                                              See get_post_type_capabilities().
 *     @type bool        $map_meta_cap          Whether to use the internal default meta capability handling.
 *                                              Default false.
 *     @type array       $supports              Core feature(s) the post type supports. Serves as an alias for calling
 *                                              add_post_type_support() directly. Core features include 'title',
 *                                              'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                              'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                              Additionally, the 'revisions' feature dictates whether the post type
 *                                              will store revisions, and the 'comments' feature dictates whether the
 *                                              comments count will show on the edit screen. Defaults is an array
 *                                              containing 'title' and 'editor'.
 *     @type callable    $register_meta_box_cb  Provide a callback function that sets up the meta boxes for the
 *                                              edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                              callback. Default null.
 *     @type array       $taxonomies            An array of taxonomy identifiers that will be registered for the
 *                                              post type. Taxonomies can be registered later with register_taxonomy()
 *                                              or register_taxonomy_for_object_type().
 *                                              Default empty array.
 *     @type bool|string $has_archive           Whether there should be post type archives, or if a string, the
 *                                              archive slug to use. Will generate the proper rewrite rules if
 *                                              $rewrite is enabled. Default false.
 *     @type bool|array  $rewrite              {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type const  $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool $query_var             Sets the query_var key for this post type. Defaults to $post_type
 *                                              key. If false, a post type cannot be loaded at
 *                                              ?{query_var}={post_slug}. If specified as a string, the query
 *                                              ?{query_var_string}={post_slug} will be valid.
 *     @type bool        $can_export            Whether to allow this post type to be exported. Default true.
 *     @type bool        $delete_with_user      Whether to delete posts of this type when deleting a user. If true,
 *                                              posts of this type belonging to the user will be moved to trash
 *                                              when then user is deleted. If false, posts of this type belonging
 *                                              to the user will *not* be trashed or deleted. If not set (the default),
 *                                              posts are trashed if post_type_supports('author'). Otherwise posts
 *                                              are not trashed or deleted. Default null.
 *     @type bool        $_builtin              FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                              "built-in" post_type. Default false.
 *     @type string      $_edit_link            FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                              this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object, or an error object.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a `WP_Post_Type` object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 4.7

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of WP_Post_Type.
 * @since 4.7.0 Introduced `show_in_rest`, 'rest_base' and 'rest_controller_class'
 *              arguments to register the post type in REST API.
 *
 * @global array $wp_post_types List of post types.
 *
 * @param string $post_type Post type key. Must not exceed 20 characters and may
 *                          only contain lowercase alphanumeric characters, dashes,
 *                          and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string      $label                 Name of the post type shown in the menu. Usually plural.
 *                                              Default is value of $labels['name'].
 *     @type array       $labels                An array of labels for this post type. If not set, post
 *                                              labels are inherited for non-hierarchical types and page
 *                                              labels for hierarchical ones. See get_post_type_labels() for a full
 *                                              list of supported labels.
 *     @type string      $description           A short descriptive summary of what the post type is.
 *                                              Default empty.
 *     @type bool        $public                Whether a post type is intended for use publicly either via
 *                                              the admin interface or by front-end users. While the default
 *                                              settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                              and $show_in_nav_menus are inherited from public, each does not
 *                                              rely on this relationship and controls a very specific intention.
 *                                              Default false.
 *     @type bool        $hierarchical          Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool        $exclude_from_search   Whether to exclude posts with this post type from front end search
 *                                              results. Default is the opposite value of $public.
 *     @type bool        $publicly_queryable    Whether queries can be performed on the front end for the post type
 *                                              as part of parse_request(). Endpoints would include:
 *                                              * ?post_type={post_type_key}
 *                                              * ?{post_type_key}={single_post_slug}
 *                                              * ?{post_type_query_var}={single_post_slug}
 *                                              If not set, the default is inherited from $public.
 *     @type bool        $show_ui               Whether to generate and allow a UI for managing this post type in the
 *                                              admin. Default is value of $public.
 *     @type bool        $show_in_menu          Where to show the post type in the admin menu. To work, $show_ui
 *                                              must be true. If true, the post type is shown in its own top level
 *                                              menu. If false, no menu is shown. If a string of an existing top
 *                                              level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                              type will be placed as a sub-menu of that.
 *                                              Default is value of $show_ui.
 *     @type bool        $show_in_nav_menus     Makes this post type available for selection in navigation menus.
 *                                              Default is value $public.
 *     @type bool        $show_in_admin_bar     Makes this post type available via the admin bar. Default is value
 *                                              of $show_in_menu.
 *     @type bool        $show_in_rest          Whether to add the post type route in the REST API 'wp/v2' namespace.
 *     @type string      $rest_base             To change the base url of REST API route. Default is $post_type.
 *     @type string      $rest_controller_class REST API Controller class name. Default is 'WP_REST_Posts_Controller'.
 *     @type int         $menu_position         The position in the menu order the post type should appear. To work,
 *                                              $show_in_menu must be true. Default null (at the bottom).
 *     @type string      $menu_icon             The url to the icon to be used for this menu. Pass a base64-encoded
 *                                              SVG using a data URI, which will be colored to match the color scheme
 *                                              -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                              of a Dashicons helper class to use a font icon, e.g.
 *                                              'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                              so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string      $capability_type       The string to use to build the read, edit, and delete capabilities.
 *                                              May be passed as an array to allow for alternative plurals when using
 *                                              this argument as a base to construct the capabilities, e.g.
 *                                              array('story', 'stories'). Default 'post'.
 *     @type array       $capabilities          Array of capabilities for this post type. $capability_type is used
 *                                              as a base to construct capabilities by default.
 *                                              See get_post_type_capabilities().
 *     @type bool        $map_meta_cap          Whether to use the internal default meta capability handling.
 *                                              Default false.
 *     @type array       $supports              Core feature(s) the post type supports. Serves as an alias for calling
 *                                              add_post_type_support() directly. Core features include 'title',
 *                                              'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                              'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                              Additionally, the 'revisions' feature dictates whether the post type
 *                                              will store revisions, and the 'comments' feature dictates whether the
 *                                              comments count will show on the edit screen. Defaults is an array
 *                                              containing 'title' and 'editor'.
 *     @type callable    $register_meta_box_cb  Provide a callback function that sets up the meta boxes for the
 *                                              edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                              callback. Default null.
 *     @type array       $taxonomies            An array of taxonomy identifiers that will be registered for the
 *                                              post type. Taxonomies can be registered later with register_taxonomy()
 *                                              or register_taxonomy_for_object_type().
 *                                              Default empty array.
 *     @type bool|string $has_archive           Whether there should be post type archives, or if a string, the
 *                                              archive slug to use. Will generate the proper rewrite rules if
 *                                              $rewrite is enabled. Default false.
 *     @type bool|array  $rewrite              {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type const  $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool $query_var             Sets the query_var key for this post type. Defaults to $post_type
 *                                              key. If false, a post type cannot be loaded at
 *                                              ?{query_var}={post_slug}. If specified as a string, the query
 *                                              ?{query_var_string}={post_slug} will be valid.
 *     @type bool        $can_export            Whether to allow this post type to be exported. Default true.
 *     @type bool        $delete_with_user      Whether to delete posts of this type when deleting a user. If true,
 *                                              posts of this type belonging to the user will be moved to trash
 *                                              when then user is deleted. If false, posts of this type belonging
 *                                              to the user will *not* be trashed or deleted. If not set (the default),
 *                                              posts are trashed if post_type_supports('author'). Otherwise posts
 *                                              are not trashed or deleted. Default null.
 *     @type bool        $_builtin              FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                              "built-in" post_type. Default false.
 *     @type string      $_edit_link            FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                              this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object, or an error object.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a WP_Post_Type object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 4.6

/**
 * Registers a post type.
 *
 * Note: Post type registrations should not be hooked before the
 * {@see 'init'} action. Also, any taxonomy connections should be
 * registered via the `$taxonomies` argument to ensure consistency
 * when hooks such as {@see 'parse_query'} or {@see 'pre_get_posts'}
 * are used.
 *
 * Post types can support any number of built-in core features such
 * as meta boxes, custom fields, post thumbnails, post statuses,
 * comments, and more. See the `$supports` argument for a complete
 * list of supported features.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing
 *              screen and post editing screen.
 * @since 4.6.0 Post type object returned is now an instance of WP_Post_Type.
 *
 * @global array $wp_post_types List of post types.
 *
 * @param string $post_type Post type key. Must not exceed 20 characters and may
 *                          only contain lowercase alphanumeric characters, dashes,
 *                          and underscores. See sanitize_key().
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string      $label                Name of the post type shown in the menu. Usually plural.
 *                                             Default is value of $labels['name'].
 *     @type array       $labels               An array of labels for this post type. If not set, post
 *                                             labels are inherited for non-hierarchical types and page
 *                                             labels for hierarchical ones. See get_post_type_labels() for a full
 *                                             list of supported labels.
 *     @type string      $description          A short descriptive summary of what the post type is.
 *                                             Default empty.
 *     @type bool        $public               Whether a post type is intended for use publicly either via
 *                                             the admin interface or by front-end users. While the default
 *                                             settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                             and $show_in_nav_menus are inherited from public, each does not
 *                                             rely on this relationship and controls a very specific intention.
 *                                             Default false.
 *     @type bool        $hierarchical         Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool        $exclude_from_search  Whether to exclude posts with this post type from front end search
 *                                             results. Default is the opposite value of $public.
 *     @type bool        $publicly_queryable   Whether queries can be performed on the front end for the post type
 *                                             as part of parse_request(). Endpoints would include:
 *                                             * ?post_type={post_type_key}
 *                                             * ?{post_type_key}={single_post_slug}
 *                                             * ?{post_type_query_var}={single_post_slug}
 *                                             If not set, the default is inherited from $public.
 *     @type bool        $show_ui              Whether to generate and allow a UI for managing this post type in the
 *                                             admin. Default is value of $public.
 *     @type bool        $show_in_menu         Where to show the post type in the admin menu. To work, $show_ui
 *                                             must be true. If true, the post type is shown in its own top level
 *                                             menu. If false, no menu is shown. If a string of an existing top
 *                                             level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                             type will be placed as a sub-menu of that.
 *                                             Default is value of $show_ui.
 *     @type bool        $show_in_nav_menus    Makes this post type available for selection in navigation menus.
 *                                             Default is value $public.
 *     @type bool        $show_in_admin_bar    Makes this post type available via the admin bar. Default is value
 *                                             of $show_in_menu.
 *     @type int         $menu_position        The position in the menu order the post type should appear. To work,
 *                                             $show_in_menu must be true. Default null (at the bottom).
 *     @type string      $menu_icon            The url to the icon to be used for this menu. Pass a base64-encoded
 *                                             SVG using a data URI, which will be colored to match the color scheme
 *                                             -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                             of a Dashicons helper class to use a font icon, e.g.
 *                                             'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                             so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string      $capability_type      The string to use to build the read, edit, and delete capabilities.
 *                                             May be passed as an array to allow for alternative plurals when using
 *                                             this argument as a base to construct the capabilities, e.g.
 *                                             array('story', 'stories'). Default 'post'.
 *     @type array       $capabilities         Array of capabilities for this post type. $capability_type is used
 *                                             as a base to construct capabilities by default.
 *                                             See get_post_type_capabilities().
 *     @type bool        $map_meta_cap         Whether to use the internal default meta capability handling.
 *                                             Default false.
 *     @type array       $supports             Core feature(s) the post type supports. Serves as an alias for calling
 *                                             add_post_type_support() directly. Core features include 'title',
 *                                             'editor', 'comments', 'revisions', 'trackbacks', 'author', 'excerpt',
 *                                             'page-attributes', 'thumbnail', 'custom-fields', and 'post-formats'.
 *                                             Additionally, the 'revisions' feature dictates whether the post type
 *                                             will store revisions, and the 'comments' feature dictates whether the
 *                                             comments count will show on the edit screen. Defaults is an array
 *                                             containing 'title' and 'editor'.
 *     @type callable    $register_meta_box_cb Provide a callback function that sets up the meta boxes for the
 *                                             edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                             callback. Default null.
 *     @type array       $taxonomies           An array of taxonomy identifiers that will be registered for the
 *                                             post type. Taxonomies can be registered later with register_taxonomy()
 *                                             or register_taxonomy_for_object_type().
 *                                             Default empty array.
 *     @type bool|string $has_archive          Whether there should be post type archives, or if a string, the
 *                                             archive slug to use. Will generate the proper rewrite rules if
 *                                             $rewrite is enabled. Default false.
 *     @type bool|array  $rewrite              {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type const  $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool $query_var            Sets the query_var key for this post type. Defaults to $post_type
 *                                             key. If false, a post type cannot be loaded at
 *                                             ?{query_var}={post_slug}. If specified as a string, the query
 *                                             ?{query_var_string}={post_slug} will be valid.
 *     @type bool        $can_export           Whether to allow this post type to be exported. Default true.
 *     @type bool        $delete_with_user     Whether to delete posts of this type when deleting a user. If true,
 *                                             posts of this type belonging to the user will be moved to trash
 *                                             when then user is deleted. If false, posts of this type belonging
 *                                             to the user will *not* be trashed or deleted. If not set (the default),
 *                                             posts are trashed if post_type_supports('author'). Otherwise posts
 *                                             are not trashed or deleted. Default null.
 *     @type bool        $_builtin             FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                             "built-in" post_type. Default false.
 *     @type string      $_edit_link           FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                             this post type. Default 'post.php?post=%d'.
 * }
 * @return WP_Post_Type|WP_Error The registered post type object, or an error object.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name
    $post_type = sanitize_key($post_type);
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2.0');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    $post_type_object = new WP_Post_Type($post_type, $args);
    $post_type_object->add_supports();
    $post_type_object->add_rewrite_rules();
    $post_type_object->register_meta_boxes();
    $wp_post_types[$post_type] = $post_type_object;
    $post_type_object->add_hooks();
    $post_type_object->register_taxonomies();
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     * @since 4.6.0 Converted the `$post_type` parameter to accept a WP_Post_Type object.
     *
     * @param string       $post_type        Post type.
     * @param WP_Post_Type $post_type_object Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $post_type_object);
    return $post_type_object;
}

WordPress Version: 4.4

/**
 * Register a post type. Do not use before init.
 *
 * A function for creating or modifying a post type based on the
 * parameters given. The function will accept an array (second optional
 * parameter), along with a string for the post type name.
 *
 * @since 2.9.0
 * @since 3.0.0 The `show_ui` argument is now enforced on the new post screen.
 * @since 4.4.0 The `show_ui` argument is now enforced on the post type listing screen and post editing screen.
 *
 * @global array      $wp_post_types List of post types.
 * @global WP_Rewrite $wp_rewrite    Used for default feeds.
 * @global WP         $wp            Used to add query vars.
 *
 * @param string $post_type Post type key, must not exceed 20 characters.
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string      $label                Name of the post type shown in the menu. Usually plural.
 *                                             Default is value of $labels['name'].
 *     @type array       $labels               An array of labels for this post type. If not set, post
 *                                             labels are inherited for non-hierarchical types and page
 *                                             labels for hierarchical ones. {@see get_post_type_labels()}.
 *     @type string      $description          A short descriptive summary of what the post type is.
 *                                             Default empty.
 *     @type bool        $public               Whether a post type is intended for use publicly either via
 *                                             the admin interface or by front-end users. While the default
 *                                             settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                             and $show_in_nav_menus are inherited from public, each does not
 *                                             rely on this relationship and controls a very specific intention.
 *                                             Default false.
 *     @type bool        $hierarchical         Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool        $exclude_from_search  Whether to exclude posts with this post type from front end search
 *                                             results. Default is the opposite value of $public.
 *     @type bool        $publicly_queryable   Whether queries can be performed on the front end for the post type
 *                                             as part of {@see parse_request()}. Endpoints would include:
 *                                             * ?post_type={post_type_key}
 *                                             * ?{post_type_key}={single_post_slug}
 *                                             * ?{post_type_query_var}={single_post_slug}
 *                                             If not set, the default is inherited from $public.
 *     @type bool        $show_ui              Whether to generate and allow a UI for managing this post type in the
 *                                             admin. Default is value of $public.
 *     @type bool        $show_in_menu         Where to show the post type in the admin menu. To work, $show_ui
 *                                             must be true. If true, the post type is shown in its own top level
 *                                             menu. If false, no menu is shown. If a string of an existing top
 *                                             level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                             type will be placed as a sub-menu of that.
 *                                             Default is value of $show_ui.
 *     @type bool        $show_in_nav_menus    Makes this post type available for selection in navigation menus.
 *                                             Default is value $public.
 *     @type bool        $show_in_admin_bar    Makes this post type available via the admin bar. Default is value
 *                                             of $show_in_menu.
 *     @type int         $menu_position        The position in the menu order the post type should appear. To work,
 *                                             $show_in_menu must be true. Default null (at the bottom).
 *     @type string      $menu_icon            The url to the icon to be used for this menu. Pass a base64-encoded
 *                                             SVG using a data URI, which will be colored to match the color scheme
 *                                             -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                             of a Dashicons helper class to use a font icon, e.g.
 *                                             'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                             so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string      $capability_type      The string to use to build the read, edit, and delete capabilities.
 *                                             May be passed as an array to allow for alternative plurals when using
 *                                             this argument as a base to construct the capabilities, e.g.
 *                                             array('story', 'stories'). Default 'post'.
 *     @type array       $capabilities         Array of capabilities for this post type. $capability_type is used
 *                                             as a base to construct capabilities by default.
 *                                             {@see get_post_type_capabilities()}.
 *     @type bool        $map_meta_cap         Whether to use the internal default meta capability handling.
 *                                             Default false.
 *     @type array       $supports             An alias for calling {@see add_post_type_support()} directly.
 *                                             Defaults to array containing 'title' & 'editor'.
 *     @type callable    $register_meta_box_cb Provide a callback function that sets up the meta boxes for the
 *                                             edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                             callback. Default null.
 *     @type array       $taxonomies           An array of taxonomy identifiers that will be registered for the
 *                                             post type. Taxonomies can be registered later with
 *                                             {@see register_taxonomy()} or {@see register_taxonomy_for_object_type()}.
 *                                             Default empty array.
 *     @type bool|string $has_archive          Whether there should be post type archives, or if a string, the
 *                                             archive slug to use. Will generate the proper rewrite rules if
 *                                             $rewrite is enabled. Default false.
 *     @type bool|array  $rewrite              {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type const  $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool $query_var            Sets the query_var key for this post type. Defaults to $post_type
 *                                             key. If false, a post type cannot be loaded at
 *                                             ?{query_var}={post_slug}. If specified as a string, the query
 *                                             ?{query_var_string}={post_slug} will be valid.
 *     @type bool        $can_export           Whether to allow this post type to be exported. Default true.
 *     @type bool        $delete_with_user     Whether to delete posts of this type when deleting a user. If true,
 *                                             posts of this type belonging to the user will be moved to trash
 *                                             when then user is deleted. If false, posts of this type belonging
 *                                             to the user will *not* be trashed or deleted. If not set (the default),
 *                                             posts are trashed if post_type_supports('author'). Otherwise posts
 *                                             are not trashed or deleted. Default null.
 *     @type bool        $_builtin             FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                             "built-in" post_type. Default false.
 *     @type string      $_edit_link           FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                             this post type. Default 'post.php?post=%d'.
 * }
 * @return object|WP_Error The registered post type object, or an error object.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types, $wp_rewrite, $wp;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Sanitize post type name
    $post_type = sanitize_key($post_type);
    $args = wp_parse_args($args);
    /**
     * Filter the arguments for registering a post type.
     *
     * @since 4.4.0
     *
     * @param array  $args      Array of arguments for registering a post type.
     * @param string $post_type Post type key.
     */
    $args = apply_filters('register_post_type_args', $args, $post_type);
    $has_edit_link = !empty($args['_edit_link']);
    // Args prefixed with an underscore are reserved for internal use.
    $defaults = array('labels' => array(), 'description' => '', 'public' => false, 'hierarchical' => false, 'exclude_from_search' => null, 'publicly_queryable' => null, 'show_ui' => null, 'show_in_menu' => null, 'show_in_nav_menus' => null, 'show_in_admin_bar' => null, 'menu_position' => null, 'menu_icon' => null, 'capability_type' => 'post', 'capabilities' => array(), 'map_meta_cap' => null, 'supports' => array(), 'register_meta_box_cb' => null, 'taxonomies' => array(), 'has_archive' => false, 'rewrite' => true, 'query_var' => true, 'can_export' => true, 'delete_with_user' => null, '_builtin' => false, '_edit_link' => 'post.php?post=%d');
    $args = array_merge($defaults, $args);
    $args = (object) $args;
    $args->name = $post_type;
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    // If not set, default to the setting for public.
    if (null === $args->publicly_queryable) {
        $args->publicly_queryable = $args->public;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_ui) {
        $args->show_ui = $args->public;
    }
    // If not set, default to the setting for show_ui.
    if (null === $args->show_in_menu || !$args->show_ui) {
        $args->show_in_menu = $args->show_ui;
    }
    // If not set, default to the whether the full UI is shown.
    if (null === $args->show_in_admin_bar) {
        $args->show_in_admin_bar = (bool) $args->show_in_menu;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_in_nav_menus) {
        $args->show_in_nav_menus = $args->public;
    }
    // If not set, default to true if not public, false if public.
    if (null === $args->exclude_from_search) {
        $args->exclude_from_search = !$args->public;
    }
    // Back compat with quirky handling in version 3.0. #14122.
    if (empty($args->capabilities) && null === $args->map_meta_cap && in_array($args->capability_type, array('post', 'page'))) {
        $args->map_meta_cap = true;
    }
    // If not set, default to false.
    if (null === $args->map_meta_cap) {
        $args->map_meta_cap = false;
    }
    // If there's no specified edit link and no UI, remove the edit link.
    if (!$args->show_ui && !$has_edit_link) {
        $args->_edit_link = '';
    }
    $args->cap = get_post_type_capabilities($args);
    unset($args->capabilities);
    if (is_array($args->capability_type)) {
        $args->capability_type = $args->capability_type[0];
    }
    if (!empty($args->supports)) {
        add_post_type_support($post_type, $args->supports);
        unset($args->supports);
    } elseif (false !== $args->supports) {
        // Add default features
        add_post_type_support($post_type, array('title', 'editor'));
    }
    if (false !== $args->query_var) {
        if (true === $args->query_var) {
            $args->query_var = $post_type;
        } else {
            $args->query_var = sanitize_title_with_dashes($args->query_var);
        }
        if ($wp && is_post_type_viewable($args)) {
            $wp->add_query_var($args->query_var);
        }
    }
    if (false !== $args->rewrite && (is_admin() || '' != get_option('permalink_structure'))) {
        if (!is_array($args->rewrite)) {
            $args->rewrite = array();
        }
        if (empty($args->rewrite['slug'])) {
            $args->rewrite['slug'] = $post_type;
        }
        if (!isset($args->rewrite['with_front'])) {
            $args->rewrite['with_front'] = true;
        }
        if (!isset($args->rewrite['pages'])) {
            $args->rewrite['pages'] = true;
        }
        if (!isset($args->rewrite['feeds']) || !$args->has_archive) {
            $args->rewrite['feeds'] = (bool) $args->has_archive;
        }
        if (!isset($args->rewrite['ep_mask'])) {
            if (isset($args->permalink_epmask)) {
                $args->rewrite['ep_mask'] = $args->permalink_epmask;
            } else {
                $args->rewrite['ep_mask'] = EP_PERMALINK;
            }
        }
        if ($args->hierarchical) {
            add_rewrite_tag("%{$post_type}%", '(.+?)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&pagename=");
        } else {
            add_rewrite_tag("%{$post_type}%", '([^/]+)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&name=");
        }
        if ($args->has_archive) {
            $archive_slug = ($args->has_archive === true) ? $args->rewrite['slug'] : $args->has_archive;
            if ($args->rewrite['with_front']) {
                $archive_slug = substr($wp_rewrite->front, 1) . $archive_slug;
            } else {
                $archive_slug = $wp_rewrite->root . $archive_slug;
            }
            add_rewrite_rule("{$archive_slug}/?\$", "index.php?post_type={$post_type}", 'top');
            if ($args->rewrite['feeds'] && $wp_rewrite->feeds) {
                $feeds = '(' . trim(implode('|', $wp_rewrite->feeds)) . ')';
                add_rewrite_rule("{$archive_slug}/feed/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
                add_rewrite_rule("{$archive_slug}/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
            }
            if ($args->rewrite['pages']) {
                add_rewrite_rule("{$archive_slug}/{$wp_rewrite->pagination_base}/([0-9]{1,})/?\$", "index.php?post_type={$post_type}" . '&paged=$matches[1]', 'top');
            }
        }
        $permastruct_args = $args->rewrite;
        $permastruct_args['feed'] = $permastruct_args['feeds'];
        add_permastruct($post_type, "{$args->rewrite['slug']}/%{$post_type}%", $permastruct_args);
    }
    // Register the post type meta box if a custom callback was specified.
    if ($args->register_meta_box_cb) {
        add_action('add_meta_boxes_' . $post_type, $args->register_meta_box_cb, 10, 1);
    }
    $args->labels = get_post_type_labels($args);
    $args->label = $args->labels->name;
    $wp_post_types[$post_type] = $args;
    add_action('future_' . $post_type, '_future_post_hook', 5, 2);
    foreach ($args->taxonomies as $taxonomy) {
        register_taxonomy_for_object_type($taxonomy, $post_type);
    }
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     *
     * @param string $post_type Post type.
     * @param object $args      Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $args);
    return $args;
}

WordPress Version: 4.2

/**
 * Register a post type. Do not use before init.
 *
 * A function for creating or modifying a post type based on the
 * parameters given. The function will accept an array (second optional
 * parameter), along with a string for the post type name.
 *
 * @since 2.9.0
 *
 * @global array      $wp_post_types List of post types.
 * @global WP_Rewrite $wp_rewrite    Used for default feeds.
 * @global WP         $wp            Used to add query vars.
 *
 * @param string $post_type Post type key, must not exceed 20 characters.
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string      $label                Name of the post type shown in the menu. Usually plural.
 *                                             Default is value of $labels['name'].
 *     @type array       $labels               An array of labels for this post type. If not set, post
 *                                             labels are inherited for non-hierarchical types and page
 *                                             labels for hierarchical ones. {@see get_post_type_labels()}.
 *     @type string      $description          A short descriptive summary of what the post type is.
 *                                             Default empty.
 *     @type bool        $public               Whether a post type is intended for use publicly either via
 *                                             the admin interface or by front-end users. While the default
 *                                             settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                             and $show_in_nav_menus are inherited from public, each does not
 *                                             rely on this relationship and controls a very specific intention.
 *                                             Default false.
 *     @type bool        $hierarchical         Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool        $exclude_from_search  Whether to exclude posts with this post type from front end search
 *                                             results. Default is the opposite value of $public.
 *     @type bool        $publicly_queryable   Whether queries can be performed on the front end for the post type
 *                                             as part of {@see parse_request()}. Endpoints would include:
 *                                             * ?post_type={post_type_key}
 *                                             * ?{post_type_key}={single_post_slug}
 *                                             * ?{post_type_query_var}={single_post_slug}
 *                                             If not set, the default is inherited from $public.
 *     @type bool        $show_ui              Whether to generate a default UI for managing this post type in the
 *                                             admin. Default is value of $public.
 *     @type bool        $show_in_menu         Where to show the post type in the admin menu. To work, $show_ui
 *                                             must be true. If true, the post type is shown in its own top level
 *                                             menu. If false, no menu is shown. If a string of an existing top
 *                                             level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                             type will be placed as a sub-menu of that.
 *                                             Default is value of $show_ui.
 *     @type bool        $show_in_nav_menus    Makes this post type available for selection in navigation menus.
 *                                             Default is value $public.
 *     @type bool        $show_in_admin_bar    Makes this post type available via the admin bar. Default is value
 *                                             of $show_in_menu.
 *     @type int         $menu_position        The position in the menu order the post type should appear. To work,
 *                                             $show_in_menu must be true. Default null (at the bottom).
 *     @type string      $menu_icon            The url to the icon to be used for this menu. Pass a base64-encoded
 *                                             SVG using a data URI, which will be colored to match the color scheme
 *                                             -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                             of a Dashicons helper class to use a font icon, e.g.
 *                                             'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                             so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string      $capability_type      The string to use to build the read, edit, and delete capabilities.
 *                                             May be passed as an array to allow for alternative plurals when using
 *                                             this argument as a base to construct the capabilities, e.g.
 *                                             array('story', 'stories'). Default 'post'.
 *     @type array       $capabilities         Array of capabilities for this post type. $capability_type is used
 *                                             as a base to construct capabilities by default.
 *                                             {@see get_post_type_capabilities()}.
 *     @type bool        $map_meta_cap         Whether to use the internal default meta capability handling.
 *                                             Default false.
 *     @type array       $supports             An alias for calling {@see add_post_type_support()} directly.
 *                                             Defaults to array containing 'title' & 'editor'.
 *     @type callback    $register_meta_box_cb Provide a callback function that sets up the meta boxes for the
 *                                             edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                             callback. Default null.
 *     @type array       $taxonomies           An array of taxonomy identifiers that will be registered for the
 *                                             post type. Taxonomies can be registered later with
 *                                             {@see register_taxonomy()} or {@see register_taxonomy_for_object_type()}.
 *                                             Default empty array.
 *     @type bool|string $has_archive          Whether there should be post type archives, or if a string, the
 *                                             archive slug to use. Will generate the proper rewrite rules if
 *                                             $rewrite is enabled. Default false.
 *     @type bool|array  $rewrite              {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type const  $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool $query_var            Sets the query_var key for this post type. Defaults to $post_type
 *                                             key. If false, a post type cannot be loaded at
 *                                             ?{query_var}={post_slug}. If specified as a string, the query
 *                                             ?{query_var_string}={post_slug} will be valid.
 *     @type bool        $can_export           Whether to allow this post type to be exported. Default true.
 *     @type bool        $delete_with_user     Whether to delete posts of this type when deleting a user. If true,
 *                                             posts of this type belonging to the user will be moved to trash
 *                                             when then user is deleted. If false, posts of this type belonging
 *                                             to the user will *not* be trashed or deleted. If not set (the default),
 *                                             posts are trashed if post_type_supports('author'). Otherwise posts
 *                                             are not trashed or deleted. Default null.
 *     @type bool        $_builtin             FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                             "built-in" post_type. Default false.
 *     @type string      $_edit_link           FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                             this post type. Default 'post.php?post=%d'.
 * }
 * @return object|WP_Error The registered post type object, or an error object.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types, $wp_rewrite, $wp;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Args prefixed with an underscore are reserved for internal use.
    $defaults = array('labels' => array(), 'description' => '', 'public' => false, 'hierarchical' => false, 'exclude_from_search' => null, 'publicly_queryable' => null, 'show_ui' => null, 'show_in_menu' => null, 'show_in_nav_menus' => null, 'show_in_admin_bar' => null, 'menu_position' => null, 'menu_icon' => null, 'capability_type' => 'post', 'capabilities' => array(), 'map_meta_cap' => null, 'supports' => array(), 'register_meta_box_cb' => null, 'taxonomies' => array(), 'has_archive' => false, 'rewrite' => true, 'query_var' => true, 'can_export' => true, 'delete_with_user' => null, '_builtin' => false, '_edit_link' => 'post.php?post=%d');
    $args = wp_parse_args($args, $defaults);
    $args = (object) $args;
    $post_type = sanitize_key($post_type);
    $args->name = $post_type;
    if (empty($post_type) || strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post type names must be between 1 and 20 characters in length.'), '4.2');
        return new WP_Error('post_type_length_invalid', __('Post type names must be between 1 and 20 characters in length.'));
    }
    // If not set, default to the setting for public.
    if (null === $args->publicly_queryable) {
        $args->publicly_queryable = $args->public;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_ui) {
        $args->show_ui = $args->public;
    }
    // If not set, default to the setting for show_ui.
    if (null === $args->show_in_menu || !$args->show_ui) {
        $args->show_in_menu = $args->show_ui;
    }
    // If not set, default to the whether the full UI is shown.
    if (null === $args->show_in_admin_bar) {
        $args->show_in_admin_bar = (bool) $args->show_in_menu;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_in_nav_menus) {
        $args->show_in_nav_menus = $args->public;
    }
    // If not set, default to true if not public, false if public.
    if (null === $args->exclude_from_search) {
        $args->exclude_from_search = !$args->public;
    }
    // Back compat with quirky handling in version 3.0. #14122.
    if (empty($args->capabilities) && null === $args->map_meta_cap && in_array($args->capability_type, array('post', 'page'))) {
        $args->map_meta_cap = true;
    }
    // If not set, default to false.
    if (null === $args->map_meta_cap) {
        $args->map_meta_cap = false;
    }
    $args->cap = get_post_type_capabilities($args);
    unset($args->capabilities);
    if (is_array($args->capability_type)) {
        $args->capability_type = $args->capability_type[0];
    }
    if (!empty($args->supports)) {
        add_post_type_support($post_type, $args->supports);
        unset($args->supports);
    } elseif (false !== $args->supports) {
        // Add default features
        add_post_type_support($post_type, array('title', 'editor'));
    }
    if (false !== $args->query_var && !empty($wp)) {
        if (true === $args->query_var) {
            $args->query_var = $post_type;
        } else {
            $args->query_var = sanitize_title_with_dashes($args->query_var);
        }
        $wp->add_query_var($args->query_var);
    }
    if (false !== $args->rewrite && (is_admin() || '' != get_option('permalink_structure'))) {
        if (!is_array($args->rewrite)) {
            $args->rewrite = array();
        }
        if (empty($args->rewrite['slug'])) {
            $args->rewrite['slug'] = $post_type;
        }
        if (!isset($args->rewrite['with_front'])) {
            $args->rewrite['with_front'] = true;
        }
        if (!isset($args->rewrite['pages'])) {
            $args->rewrite['pages'] = true;
        }
        if (!isset($args->rewrite['feeds']) || !$args->has_archive) {
            $args->rewrite['feeds'] = (bool) $args->has_archive;
        }
        if (!isset($args->rewrite['ep_mask'])) {
            if (isset($args->permalink_epmask)) {
                $args->rewrite['ep_mask'] = $args->permalink_epmask;
            } else {
                $args->rewrite['ep_mask'] = EP_PERMALINK;
            }
        }
        if ($args->hierarchical) {
            add_rewrite_tag("%{$post_type}%", '(.+?)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&pagename=");
        } else {
            add_rewrite_tag("%{$post_type}%", '([^/]+)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&name=");
        }
        if ($args->has_archive) {
            $archive_slug = ($args->has_archive === true) ? $args->rewrite['slug'] : $args->has_archive;
            if ($args->rewrite['with_front']) {
                $archive_slug = substr($wp_rewrite->front, 1) . $archive_slug;
            } else {
                $archive_slug = $wp_rewrite->root . $archive_slug;
            }
            add_rewrite_rule("{$archive_slug}/?\$", "index.php?post_type={$post_type}", 'top');
            if ($args->rewrite['feeds'] && $wp_rewrite->feeds) {
                $feeds = '(' . trim(implode('|', $wp_rewrite->feeds)) . ')';
                add_rewrite_rule("{$archive_slug}/feed/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
                add_rewrite_rule("{$archive_slug}/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
            }
            if ($args->rewrite['pages']) {
                add_rewrite_rule("{$archive_slug}/{$wp_rewrite->pagination_base}/([0-9]{1,})/?\$", "index.php?post_type={$post_type}" . '&paged=$matches[1]', 'top');
            }
        }
        $permastruct_args = $args->rewrite;
        $permastruct_args['feed'] = $permastruct_args['feeds'];
        add_permastruct($post_type, "{$args->rewrite['slug']}/%{$post_type}%", $permastruct_args);
    }
    // Register the post type meta box if a custom callback was specified.
    if ($args->register_meta_box_cb) {
        add_action('add_meta_boxes_' . $post_type, $args->register_meta_box_cb, 10, 1);
    }
    $args->labels = get_post_type_labels($args);
    $args->label = $args->labels->name;
    $wp_post_types[$post_type] = $args;
    add_action('future_' . $post_type, '_future_post_hook', 5, 2);
    foreach ($args->taxonomies as $taxonomy) {
        register_taxonomy_for_object_type($taxonomy, $post_type);
    }
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     *
     * @param string $post_type Post type.
     * @param object $args      Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $args);
    return $args;
}

WordPress Version: 4.1

/**
 * Register a post type. Do not use before init.
 *
 * A function for creating or modifying a post type based on the
 * parameters given. The function will accept an array (second optional
 * parameter), along with a string for the post type name.
 *
 * @since 2.9.0
 *
 * @global array      $wp_post_types List of post types.
 * @global WP_Rewrite $wp_rewrite    Used for default feeds.
 * @global WP         $wp            Used to add query vars.
 *
 * @param string $post_type Post type key, must not exceed 20 characters.
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string      $label                Name of the post type shown in the menu. Usually plural.
 *                                             Default is value of $labels['name'].
 *     @type array       $labels               An array of labels for this post type. If not set, post
 *                                             labels are inherited for non-hierarchical types and page
 *                                             labels for hierarchical ones. {@see get_post_type_labels()}.
 *     @type string      $description          A short descriptive summary of what the post type is.
 *                                             Default empty.
 *     @type bool        $public               Whether a post type is intended for use publicly either via
 *                                             the admin interface or by front-end users. While the default
 *                                             settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                             and $show_in_nav_menus are inherited from public, each does not
 *                                             rely on this relationship and controls a very specific intention.
 *                                             Default false.
 *     @type bool        $hierarchical         Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool        $exclude_from_search  Whether to exclude posts with this post type from front end search
 *                                             results. Default is the opposite value of $public.
 *     @type bool        $publicly_queryable   Whether queries can be performed on the front end for the post type
 *                                             as part of {@see parse_request()}. Endpoints would include:
 *                                             * ?post_type={post_type_key}
 *                                             * ?{post_type_key}={single_post_slug}
 *                                             * ?{post_type_query_var}={single_post_slug}
 *                                             If not set, the default is inherited from $public.
 *     @type bool        $show_ui              Whether to generate a default UI for managing this post type in the
 *                                             admin. Default is value of $public.
 *     @type bool        $show_in_menu         Where to show the post type in the admin menu. To work, $show_ui
 *                                             must be true. If true, the post type is shown in its own top level
 *                                             menu. If false, no menu is shown. If a string of an existing top
 *                                             level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                             type will be placed as a sub-menu of that.
 *                                             Default is value of $show_ui.
 *     @type bool        $show_in_nav_menus    Makes this post type available for selection in navigation menus.
 *                                             Default is value $public.
 *     @type bool        $show_in_admin_bar    Makes this post type available via the admin bar. Default is value
 *                                             of $show_in_menu.
 *     @type int         $menu_position        The position in the menu order the post type should appear. To work,
 *                                             $show_in_menu must be true. Default null (at the bottom).
 *     @type string      $menu_icon            The url to the icon to be used for this menu. Pass a base64-encoded
 *                                             SVG using a data URI, which will be colored to match the color scheme
 *                                             -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                             of a Dashicons helper class to use a font icon, e.g.
 *                                             'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                             so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string      $capability_type      The string to use to build the read, edit, and delete capabilities.
 *                                             May be passed as an array to allow for alternative plurals when using
 *                                             this argument as a base to construct the capabilities, e.g.
 *                                             array('story', 'stories'). Default 'post'.
 *     @type array       $capabilities         Array of capabilities for this post type. $capability_type is used
 *                                             as a base to construct capabilities by default.
 *                                             {@see get_post_type_capabilities()}.
 *     @type bool        $map_meta_cap         Whether to use the internal default meta capability handling.
 *                                             Default false.
 *     @type array       $supports             An alias for calling {@see add_post_type_support()} directly.
 *                                             Defaults to array containing 'title' & 'editor'.
 *     @type callback    $register_meta_box_cb Provide a callback function that sets up the meta boxes for the
 *                                             edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                             callback. Default null.
 *     @type array       $taxonomies           An array of taxonomy identifiers that will be registered for the
 *                                             post type. Taxonomies can be registered later with
 *                                             {@see register_taxonomy()} or {@see register_taxonomy_for_object_type()}.
 *                                             Default empty array.
 *     @type bool|string $has_archive          Whether there should be post type archives, or if a string, the
 *                                             archive slug to use. Will generate the proper rewrite rules if
 *                                             $rewrite is enabled. Default false.
 *     @type bool|array  $rewrite              {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type const  $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool $query_var            Sets the query_var key for this post type. Defaults to $post_type
 *                                             key. If false, a post type cannot be loaded at
 *                                             ?{query_var}={post_slug}. If specified as a string, the query
 *                                             ?{query_var_string}={post_slug} will be valid.
 *     @type bool        $can_export           Whether to allow this post type to be exported. Default true.
 *     @type bool        $delete_with_user     Whether to delete posts of this type when deleting a user. If true,
 *                                             posts of this type belonging to the user will be moved to trash
 *                                             when then user is deleted. If false, posts of this type belonging
 *                                             to the user will *not* be trashed or deleted. If not set (the default),
 *                                             posts are trashed if post_type_supports('author'). Otherwise posts
 *                                             are not trashed or deleted. Default null.
 *     @type bool        $_builtin             FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                             "built-in" post_type. Default false.
 *     @type string      $_edit_link           FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                             this post type. Default 'post.php?post=%d'.
 * }
 * @return object|WP_Error The registered post type object, or an error object.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types, $wp_rewrite, $wp;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Args prefixed with an underscore are reserved for internal use.
    $defaults = array('labels' => array(), 'description' => '', 'public' => false, 'hierarchical' => false, 'exclude_from_search' => null, 'publicly_queryable' => null, 'show_ui' => null, 'show_in_menu' => null, 'show_in_nav_menus' => null, 'show_in_admin_bar' => null, 'menu_position' => null, 'menu_icon' => null, 'capability_type' => 'post', 'capabilities' => array(), 'map_meta_cap' => null, 'supports' => array(), 'register_meta_box_cb' => null, 'taxonomies' => array(), 'has_archive' => false, 'rewrite' => true, 'query_var' => true, 'can_export' => true, 'delete_with_user' => null, '_builtin' => false, '_edit_link' => 'post.php?post=%d');
    $args = wp_parse_args($args, $defaults);
    $args = (object) $args;
    $post_type = sanitize_key($post_type);
    $args->name = $post_type;
    if (strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post types cannot exceed 20 characters in length'), '4.0');
        return new WP_Error('post_type_too_long', __('Post types cannot exceed 20 characters in length'));
    }
    // If not set, default to the setting for public.
    if (null === $args->publicly_queryable) {
        $args->publicly_queryable = $args->public;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_ui) {
        $args->show_ui = $args->public;
    }
    // If not set, default to the setting for show_ui.
    if (null === $args->show_in_menu || !$args->show_ui) {
        $args->show_in_menu = $args->show_ui;
    }
    // If not set, default to the whether the full UI is shown.
    if (null === $args->show_in_admin_bar) {
        $args->show_in_admin_bar = (bool) $args->show_in_menu;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_in_nav_menus) {
        $args->show_in_nav_menus = $args->public;
    }
    // If not set, default to true if not public, false if public.
    if (null === $args->exclude_from_search) {
        $args->exclude_from_search = !$args->public;
    }
    // Back compat with quirky handling in version 3.0. #14122.
    if (empty($args->capabilities) && null === $args->map_meta_cap && in_array($args->capability_type, array('post', 'page'))) {
        $args->map_meta_cap = true;
    }
    // If not set, default to false.
    if (null === $args->map_meta_cap) {
        $args->map_meta_cap = false;
    }
    $args->cap = get_post_type_capabilities($args);
    unset($args->capabilities);
    if (is_array($args->capability_type)) {
        $args->capability_type = $args->capability_type[0];
    }
    if (!empty($args->supports)) {
        add_post_type_support($post_type, $args->supports);
        unset($args->supports);
    } elseif (false !== $args->supports) {
        // Add default features
        add_post_type_support($post_type, array('title', 'editor'));
    }
    if (false !== $args->query_var && !empty($wp)) {
        if (true === $args->query_var) {
            $args->query_var = $post_type;
        } else {
            $args->query_var = sanitize_title_with_dashes($args->query_var);
        }
        $wp->add_query_var($args->query_var);
    }
    if (false !== $args->rewrite && (is_admin() || '' != get_option('permalink_structure'))) {
        if (!is_array($args->rewrite)) {
            $args->rewrite = array();
        }
        if (empty($args->rewrite['slug'])) {
            $args->rewrite['slug'] = $post_type;
        }
        if (!isset($args->rewrite['with_front'])) {
            $args->rewrite['with_front'] = true;
        }
        if (!isset($args->rewrite['pages'])) {
            $args->rewrite['pages'] = true;
        }
        if (!isset($args->rewrite['feeds']) || !$args->has_archive) {
            $args->rewrite['feeds'] = (bool) $args->has_archive;
        }
        if (!isset($args->rewrite['ep_mask'])) {
            if (isset($args->permalink_epmask)) {
                $args->rewrite['ep_mask'] = $args->permalink_epmask;
            } else {
                $args->rewrite['ep_mask'] = EP_PERMALINK;
            }
        }
        if ($args->hierarchical) {
            add_rewrite_tag("%{$post_type}%", '(.+?)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&pagename=");
        } else {
            add_rewrite_tag("%{$post_type}%", '([^/]+)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&name=");
        }
        if ($args->has_archive) {
            $archive_slug = ($args->has_archive === true) ? $args->rewrite['slug'] : $args->has_archive;
            if ($args->rewrite['with_front']) {
                $archive_slug = substr($wp_rewrite->front, 1) . $archive_slug;
            } else {
                $archive_slug = $wp_rewrite->root . $archive_slug;
            }
            add_rewrite_rule("{$archive_slug}/?\$", "index.php?post_type={$post_type}", 'top');
            if ($args->rewrite['feeds'] && $wp_rewrite->feeds) {
                $feeds = '(' . trim(implode('|', $wp_rewrite->feeds)) . ')';
                add_rewrite_rule("{$archive_slug}/feed/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
                add_rewrite_rule("{$archive_slug}/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
            }
            if ($args->rewrite['pages']) {
                add_rewrite_rule("{$archive_slug}/{$wp_rewrite->pagination_base}/([0-9]{1,})/?\$", "index.php?post_type={$post_type}" . '&paged=$matches[1]', 'top');
            }
        }
        $permastruct_args = $args->rewrite;
        $permastruct_args['feed'] = $permastruct_args['feeds'];
        add_permastruct($post_type, "{$args->rewrite['slug']}/%{$post_type}%", $permastruct_args);
    }
    // Register the post type meta box if a custom callback was specified.
    if ($args->register_meta_box_cb) {
        add_action('add_meta_boxes_' . $post_type, $args->register_meta_box_cb, 10, 1);
    }
    $args->labels = get_post_type_labels($args);
    $args->label = $args->labels->name;
    $wp_post_types[$post_type] = $args;
    add_action('future_' . $post_type, '_future_post_hook', 5, 2);
    foreach ($args->taxonomies as $taxonomy) {
        register_taxonomy_for_object_type($taxonomy, $post_type);
    }
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     *
     * @param string $post_type Post type.
     * @param object $args      Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $args);
    return $args;
}

WordPress Version: 4.0

/**
 * Register a post type. Do not use before init.
 *
 * A function for creating or modifying a post type based on the
 * parameters given. The function will accept an array (second optional
 * parameter), along with a string for the post type name.
 *
 * @since 2.9.0
 *
 * @global array      $wp_post_types List of post types.
 * @global WP_Rewrite $wp_rewrite    Used for default feeds.
 * @global WP         $wp            Used to add query vars.
 *
 * @param string $post_type Post type key, must not exceed 20 characters.
 * @param array|string $args {
 *     Array or string of arguments for registering a post type.
 *
 *     @type string      $label                Name of the post type shown in the menu. Usually plural.
 *                                             Default is value of $labels['name'].
 *     @type array       $labels               An array of labels for this post type. If not set, post
 *                                             labels are inherited for non-hierarchical types and page
 *                                             labels for hierarchical ones. {@see get_post_type_labels()}.
 *     @type string      $description          A short descriptive summary of what the post type is.
 *                                             Default empty.
 *     @type bool        $public               Whether a post type is intended for use publicly either via
 *                                             the admin interface or by front-end users. While the default
 *                                             settings of $exclude_from_search, $publicly_queryable, $show_ui,
 *                                             and $show_in_nav_menus are inherited from public, each does not
 *                                             rely on this relationship and controls a very specific intention.
 *                                             Default false.
 *     @type bool        $hierarchical         Whether the post type is hierarchical (e.g. page). Default false.
 *     @type bool        $exclude_from_search  Whether to exclude posts with this post type from front end search
 *                                             results. Default is the opposite value of $public.
 *     @type bool        $publicly_queryable   Whether queries can be performed on the front end for the post type
 *                                             as part of {@see parse_request()}. Endpoints would include:
 *                                             * ?post_type={post_type_key}
 *                                             * ?{post_type_key}={single_post_slug}
 *                                             * ?{post_type_query_var}={single_post_slug}
 *                                             If not set, the default is inherited from $public.
 *     @type bool        $show_ui              Whether to generate a default UI for managing this post type in the
 *                                             admin. Default is value of $public.
 *     @type bool        $show_in_menu         Where to show the post type in the admin menu. To work, $show_ui
 *                                             must be true. If true, the post type is shown in its own top level
 *                                             menu. If false, no menu is shown. If a string of an existing top
 *                                             level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post
 *                                             type will be placed as a sub-menu of that.
 *                                             Default is value of $show_ui.
 *     @type bool        $show_in_nav_menus    Makes this post type available for selection in navigation menus.
 *                                             Default is value $public.
 *     @type bool        $show_in_admin_bar    Makes this post type available via the admin bar. Default is value
 *                                             of $show_in_menu.
 *     @type int         $menu_position        The position in the menu order the post type should appear. To work,
 *                                             $show_in_menu must be true. Default null (at the bottom).
 *     @type string      $menu_icon            The url to the icon to be used for this menu. Pass a base64-encoded
 *                                             SVG using a data URI, which will be colored to match the color scheme
 *                                             -- this should begin with 'data:image/svg+xml;base64,'. Pass the name
 *                                             of a Dashicons helper class to use a font icon, e.g.
 *                                             'dashicons-chart-pie'. Pass 'none' to leave div.wp-menu-image empty
 *                                             so an icon can be added via CSS. Defaults to use the posts icon.
 *     @type string      $capability_type      The string to use to build the read, edit, and delete capabilities.
 *                                             May be passed as an array to allow for alternative plurals when using
 *                                             this argument as a base to construct the capabilities, e.g.
 *                                             array('story', 'stories'). Default 'post'.
 *     @type array       $capabilities         Array of capabilities for this post type. $capability_type is used
 *                                             as a base to construct capabilities by default.
 *                                             {@see get_post_type_capabilities()}.
 *     @type bool        $map_meta_cap         Whether to use the internal default meta capability handling.
 *                                             Default false.
 *     @type array       $supports             An alias for calling {@see add_post_type_support()} directly.
 *                                             Defaults to array containing 'title' & 'editor'.
 *     @type callback    $register_meta_box_cb Provide a callback function that sets up the meta boxes for the
 *                                             edit form. Do remove_meta_box() and add_meta_box() calls in the
 *                                             callback. Default null.
 *     @type array       $taxonomies           An array of taxonomy identifiers that will be registered for the
 *                                             post type. Taxonomies can be registered later with
 *                                             {@see register_taxonomy()} or {@see register_taxonomy_for_object_type()}.
 *                                             Default empty array.
 *     @type bool|string $has_archive          Whether there should be post type archives, or if a string, the
 *                                             archive slug to use. Will generate the proper rewrite rules if
 *                                             $rewrite is enabled. Default false.
 *     @type bool|array  $rewrite              {
 *         Triggers the handling of rewrites for this post type. To prevent rewrite, set to false.
 *         Defaults to true, using $post_type as slug. To specify rewrite rules, an array can be
 *         passed with any of these keys:
 *
 *         @type string $slug       Customize the permastruct slug. Defaults to $post_type key.
 *         @type bool   $with_front Whether the permastruct should be prepended with WP_Rewrite::$front.
 *                                  Default true.
 *         @type bool   $feeds      Whether the feed permastruct should be built for this post type.
 *                                  Default is value of $has_archive.
 *         @type bool   $pages      Whether the permastruct should provide for pagination. Default true.
 *         @type const  $ep_mask    Endpoint mask to assign. If not specified and permalink_epmask is set,
 *                                  inherits from $permalink_epmask. If not specified and permalink_epmask
 *                                  is not set, defaults to EP_PERMALINK.
 *     }
 *     @type string|bool $query_var            Sets the query_var key for this post type. Defaults to $post_type
 *                                             key. If false, a post type cannot be loaded at
 *                                             ?{query_var}={post_slug}. If specified as a string, the query
 *                                             ?{query_var_string}={post_slug} will be valid.
 *     @type bool        $can_export           Whether to allow this post type to be exported. Default true.
 *     @type bool        $delete_with_user     Whether to delete posts of this type when deleting a user. If true,
 *                                             posts of this type belonging to the user will be moved to trash
 *                                             when then user is deleted. If false, posts of this type belonging
 *                                             to the user will *not* be trashed or deleted. If not set (the default),
 *                                             posts are trashed if post_type_supports('author'). Otherwise posts
 *                                             are not trashed or deleted. Default null.
 *     @type bool        $_builtin             FOR INTERNAL USE ONLY! True if this post type is a native or
 *                                             "built-in" post_type. Default false.
 *     @type string      $_edit_link           FOR INTERNAL USE ONLY! URL segment to use for edit link of
 *                                             this post type. Default 'post.php?post=%d'.
 * }
 * @return object|WP_Error The registered post type object, or an error object.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types, $wp_rewrite, $wp;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Args prefixed with an underscore are reserved for internal use.
    $defaults = array('labels' => array(), 'description' => '', 'public' => false, 'hierarchical' => false, 'exclude_from_search' => null, 'publicly_queryable' => null, 'show_ui' => null, 'show_in_menu' => null, 'show_in_nav_menus' => null, 'show_in_admin_bar' => null, 'menu_position' => null, 'menu_icon' => null, 'capability_type' => 'post', 'capabilities' => array(), 'map_meta_cap' => null, 'supports' => array(), 'register_meta_box_cb' => null, 'taxonomies' => array(), 'has_archive' => false, 'rewrite' => true, 'query_var' => true, 'can_export' => true, 'delete_with_user' => null, '_builtin' => false, '_edit_link' => 'post.php?post=%d');
    $args = wp_parse_args($args, $defaults);
    $args = (object) $args;
    $post_type = sanitize_key($post_type);
    $args->name = $post_type;
    if (strlen($post_type) > 20) {
        _doing_it_wrong(__FUNCTION__, __('Post types cannot exceed 20 characters in length'), '4.0');
        return new WP_Error('post_type_too_long', __('Post types cannot exceed 20 characters in length'));
    }
    // If not set, default to the setting for public.
    if (null === $args->publicly_queryable) {
        $args->publicly_queryable = $args->public;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_ui) {
        $args->show_ui = $args->public;
    }
    // If not set, default to the setting for show_ui.
    if (null === $args->show_in_menu || !$args->show_ui) {
        $args->show_in_menu = $args->show_ui;
    }
    // If not set, default to the whether the full UI is shown.
    if (null === $args->show_in_admin_bar) {
        $args->show_in_admin_bar = true === $args->show_in_menu;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_in_nav_menus) {
        $args->show_in_nav_menus = $args->public;
    }
    // If not set, default to true if not public, false if public.
    if (null === $args->exclude_from_search) {
        $args->exclude_from_search = !$args->public;
    }
    // Back compat with quirky handling in version 3.0. #14122.
    if (empty($args->capabilities) && null === $args->map_meta_cap && in_array($args->capability_type, array('post', 'page'))) {
        $args->map_meta_cap = true;
    }
    // If not set, default to false.
    if (null === $args->map_meta_cap) {
        $args->map_meta_cap = false;
    }
    $args->cap = get_post_type_capabilities($args);
    unset($args->capabilities);
    if (is_array($args->capability_type)) {
        $args->capability_type = $args->capability_type[0];
    }
    if (!empty($args->supports)) {
        add_post_type_support($post_type, $args->supports);
        unset($args->supports);
    } elseif (false !== $args->supports) {
        // Add default features
        add_post_type_support($post_type, array('title', 'editor'));
    }
    if (false !== $args->query_var && !empty($wp)) {
        if (true === $args->query_var) {
            $args->query_var = $post_type;
        } else {
            $args->query_var = sanitize_title_with_dashes($args->query_var);
        }
        $wp->add_query_var($args->query_var);
    }
    if (false !== $args->rewrite && (is_admin() || '' != get_option('permalink_structure'))) {
        if (!is_array($args->rewrite)) {
            $args->rewrite = array();
        }
        if (empty($args->rewrite['slug'])) {
            $args->rewrite['slug'] = $post_type;
        }
        if (!isset($args->rewrite['with_front'])) {
            $args->rewrite['with_front'] = true;
        }
        if (!isset($args->rewrite['pages'])) {
            $args->rewrite['pages'] = true;
        }
        if (!isset($args->rewrite['feeds']) || !$args->has_archive) {
            $args->rewrite['feeds'] = (bool) $args->has_archive;
        }
        if (!isset($args->rewrite['ep_mask'])) {
            if (isset($args->permalink_epmask)) {
                $args->rewrite['ep_mask'] = $args->permalink_epmask;
            } else {
                $args->rewrite['ep_mask'] = EP_PERMALINK;
            }
        }
        if ($args->hierarchical) {
            add_rewrite_tag("%{$post_type}%", '(.+?)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&pagename=");
        } else {
            add_rewrite_tag("%{$post_type}%", '([^/]+)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&name=");
        }
        if ($args->has_archive) {
            $archive_slug = ($args->has_archive === true) ? $args->rewrite['slug'] : $args->has_archive;
            if ($args->rewrite['with_front']) {
                $archive_slug = substr($wp_rewrite->front, 1) . $archive_slug;
            } else {
                $archive_slug = $wp_rewrite->root . $archive_slug;
            }
            add_rewrite_rule("{$archive_slug}/?\$", "index.php?post_type={$post_type}", 'top');
            if ($args->rewrite['feeds'] && $wp_rewrite->feeds) {
                $feeds = '(' . trim(implode('|', $wp_rewrite->feeds)) . ')';
                add_rewrite_rule("{$archive_slug}/feed/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
                add_rewrite_rule("{$archive_slug}/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
            }
            if ($args->rewrite['pages']) {
                add_rewrite_rule("{$archive_slug}/{$wp_rewrite->pagination_base}/([0-9]{1,})/?\$", "index.php?post_type={$post_type}" . '&paged=$matches[1]', 'top');
            }
        }
        $permastruct_args = $args->rewrite;
        $permastruct_args['feed'] = $permastruct_args['feeds'];
        add_permastruct($post_type, "{$args->rewrite['slug']}/%{$post_type}%", $permastruct_args);
    }
    // Register the post type meta box if a custom callback was specified.
    if ($args->register_meta_box_cb) {
        add_action('add_meta_boxes_' . $post_type, $args->register_meta_box_cb, 10, 1);
    }
    $args->labels = get_post_type_labels($args);
    $args->label = $args->labels->name;
    $wp_post_types[$post_type] = $args;
    add_action('future_' . $post_type, '_future_post_hook', 5, 2);
    foreach ($args->taxonomies as $taxonomy) {
        register_taxonomy_for_object_type($taxonomy, $post_type);
    }
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     *
     * @param string $post_type Post type.
     * @param object $args      Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $args);
    return $args;
}

WordPress Version: 3.9

/**
 * Register a post type. Do not use before init.
 *
 * A function for creating or modifying a post type based on the
 * parameters given. The function will accept an array (second optional
 * parameter), along with a string for the post type name.
 *
 * Optional $args contents:
 *
 * - label - Name of the post type shown in the menu. Usually plural. If not set, labels['name'] will be used.
 * - labels - An array of labels for this post type.
 *     * If not set, post labels are inherited for non-hierarchical types and page labels for hierarchical ones.
 *     * You can see accepted values in {@link get_post_type_labels()}.
 * - description - A short descriptive summary of what the post type is. Defaults to blank.
 * - public - Whether a post type is intended for use publicly either via the admin interface or by front-end users.
 *     * Defaults to false.
 *     * While the default settings of exclude_from_search, publicly_queryable, show_ui, and show_in_nav_menus are
 *       inherited from public, each does not rely on this relationship and controls a very specific intention.
 * - hierarchical - Whether the post type is hierarchical (e.g. page). Defaults to false.
 * - exclude_from_search - Whether to exclude posts with this post type from front end search results.
 *     * If not set, the opposite of public's current value is used.
 * - publicly_queryable - Whether queries can be performed on the front end for the post type as part of parse_request().
 *     * ?post_type={post_type_key}
 *     * ?{post_type_key}={single_post_slug}
 *     * ?{post_type_query_var}={single_post_slug}
 *     * If not set, the default is inherited from public.
 * - show_ui - Whether to generate a default UI for managing this post type in the admin.
 *     * If not set, the default is inherited from public.
 * - show_in_menu - Where to show the post type in the admin menu.
 *     * If true, the post type is shown in its own top level menu.
 *     * If false, no menu is shown
 *     * If a string of an existing top level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post type will
 *       be placed as a sub menu of that.
 *     * show_ui must be true.
 *     * If not set, the default is inherited from show_ui
 * - show_in_nav_menus - Makes this post type available for selection in navigation menus.
 *     * If not set, the default is inherited from public.
 * - show_in_admin_bar - Makes this post type available via the admin bar.
 *     * If not set, the default is inherited from show_in_menu
 * - menu_position - The position in the menu order the post type should appear.
 *     * show_in_menu must be true
 *     * Defaults to null, which places it at the bottom of its area.
 * - menu_icon - The url to the icon to be used for this menu. Defaults to use the posts icon.
 *     * Pass a base64-encoded SVG using a data URI, which will be colored to match the color scheme.
 *      This should begin with 'data:image/svg+xml;base64,'.
 *     * Pass the name of a Dashicons helper class to use a font icon, e.g. 'dashicons-chart-pie'.
 *     * Pass 'none' to leave div.wp-menu-image empty so an icon can be added via CSS.
 * - capability_type - The string to use to build the read, edit, and delete capabilities. Defaults to 'post'.
 *     * May be passed as an array to allow for alternative plurals when using this argument as a base to construct the
 *       capabilities, e.g. array('story', 'stories').
 * - capabilities - Array of capabilities for this post type.
 *     * By default the capability_type is used as a base to construct capabilities.
 *     * You can see accepted values in {@link get_post_type_capabilities()}.
 * - map_meta_cap - Whether to use the internal default meta capability handling. Defaults to false.
 * - supports - An alias for calling add_post_type_support() directly. Defaults to title and editor.
 *     * See {@link add_post_type_support()} for documentation.
 * - register_meta_box_cb - Provide a callback function that sets up the meta boxes
 *     for the edit form. Do remove_meta_box() and add_meta_box() calls in the callback.
 * - taxonomies - An array of taxonomy identifiers that will be registered for the post type.
 *     * Default is no taxonomies.
 *     * Taxonomies can be registered later with register_taxonomy() or register_taxonomy_for_object_type().
 * - has_archive - True to enable post type archives. Default is false.
 *     * Will generate the proper rewrite rules if rewrite is enabled.
 * - rewrite - Triggers the handling of rewrites for this post type. Defaults to true, using $post_type as slug.
 *     * To prevent rewrite, set to false.
 *     * To specify rewrite rules, an array can be passed with any of these keys
 *         * 'slug' => string Customize the permastruct slug. Defaults to $post_type key
 *         * 'with_front' => bool Should the permastruct be prepended with WP_Rewrite::$front. Defaults to true.
 *         * 'feeds' => bool Should a feed permastruct be built for this post type. Inherits default from has_archive.
 *         * 'pages' => bool Should the permastruct provide for pagination. Defaults to true.
 *         * 'ep_mask' => const Assign an endpoint mask.
 *             * If not specified and permalink_epmask is set, inherits from permalink_epmask.
 *             * If not specified and permalink_epmask is not set, defaults to EP_PERMALINK
 * - query_var - Sets the query_var key for this post type. Defaults to $post_type key
 *     * If false, a post type cannot be loaded at ?{query_var}={post_slug}
 *     * If specified as a string, the query ?{query_var_string}={post_slug} will be valid.
 * - can_export - Allows this post type to be exported. Defaults to true.
 * - delete_with_user - Whether to delete posts of this type when deleting a user.
 *     * If true, posts of this type belonging to the user will be moved to trash when then user is deleted.
 *     * If false, posts of this type belonging to the user will *not* be trashed or deleted.
 *     * If not set (the default), posts are trashed if post_type_supports('author'). Otherwise posts are not trashed or deleted.
 * - _builtin - true if this post type is a native or "built-in" post_type. THIS IS FOR INTERNAL USE ONLY!
 * - _edit_link - URL segement to use for edit link of this post type. THIS IS FOR INTERNAL USE ONLY!
 *
 * @since 2.9.0
 * @uses $wp_post_types Inserts new post type object into the list
 * @uses $wp_rewrite Gets default feeds
 * @uses $wp Adds query vars
 *
 * @param string $post_type Post type key, must not exceed 20 characters.
 * @param array|string $args See optional args description above.
 * @return object|WP_Error the registered post type object, or an error object.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types, $wp_rewrite, $wp;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Args prefixed with an underscore are reserved for internal use.
    $defaults = array('labels' => array(), 'description' => '', 'public' => false, 'hierarchical' => false, 'exclude_from_search' => null, 'publicly_queryable' => null, 'show_ui' => null, 'show_in_menu' => null, 'show_in_nav_menus' => null, 'show_in_admin_bar' => null, 'menu_position' => null, 'menu_icon' => null, 'capability_type' => 'post', 'capabilities' => array(), 'map_meta_cap' => null, 'supports' => array(), 'register_meta_box_cb' => null, 'taxonomies' => array(), 'has_archive' => false, 'rewrite' => true, 'query_var' => true, 'can_export' => true, 'delete_with_user' => null, '_builtin' => false, '_edit_link' => 'post.php?post=%d');
    $args = wp_parse_args($args, $defaults);
    $args = (object) $args;
    $post_type = sanitize_key($post_type);
    $args->name = $post_type;
    if (strlen($post_type) > 20) {
        return new WP_Error('post_type_too_long', __('Post types cannot exceed 20 characters in length'));
    }
    // If not set, default to the setting for public.
    if (null === $args->publicly_queryable) {
        $args->publicly_queryable = $args->public;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_ui) {
        $args->show_ui = $args->public;
    }
    // If not set, default to the setting for show_ui.
    if (null === $args->show_in_menu || !$args->show_ui) {
        $args->show_in_menu = $args->show_ui;
    }
    // If not set, default to the whether the full UI is shown.
    if (null === $args->show_in_admin_bar) {
        $args->show_in_admin_bar = true === $args->show_in_menu;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_in_nav_menus) {
        $args->show_in_nav_menus = $args->public;
    }
    // If not set, default to true if not public, false if public.
    if (null === $args->exclude_from_search) {
        $args->exclude_from_search = !$args->public;
    }
    // Back compat with quirky handling in version 3.0. #14122
    if (empty($args->capabilities) && null === $args->map_meta_cap && in_array($args->capability_type, array('post', 'page'))) {
        $args->map_meta_cap = true;
    }
    // If not set, default to false.
    if (null === $args->map_meta_cap) {
        $args->map_meta_cap = false;
    }
    $args->cap = get_post_type_capabilities($args);
    unset($args->capabilities);
    if (is_array($args->capability_type)) {
        $args->capability_type = $args->capability_type[0];
    }
    if (!empty($args->supports)) {
        add_post_type_support($post_type, $args->supports);
        unset($args->supports);
    } elseif (false !== $args->supports) {
        // Add default features
        add_post_type_support($post_type, array('title', 'editor'));
    }
    if (false !== $args->query_var && !empty($wp)) {
        if (true === $args->query_var) {
            $args->query_var = $post_type;
        } else {
            $args->query_var = sanitize_title_with_dashes($args->query_var);
        }
        $wp->add_query_var($args->query_var);
    }
    if (false !== $args->rewrite && (is_admin() || '' != get_option('permalink_structure'))) {
        if (!is_array($args->rewrite)) {
            $args->rewrite = array();
        }
        if (empty($args->rewrite['slug'])) {
            $args->rewrite['slug'] = $post_type;
        }
        if (!isset($args->rewrite['with_front'])) {
            $args->rewrite['with_front'] = true;
        }
        if (!isset($args->rewrite['pages'])) {
            $args->rewrite['pages'] = true;
        }
        if (!isset($args->rewrite['feeds']) || !$args->has_archive) {
            $args->rewrite['feeds'] = (bool) $args->has_archive;
        }
        if (!isset($args->rewrite['ep_mask'])) {
            if (isset($args->permalink_epmask)) {
                $args->rewrite['ep_mask'] = $args->permalink_epmask;
            } else {
                $args->rewrite['ep_mask'] = EP_PERMALINK;
            }
        }
        if ($args->hierarchical) {
            add_rewrite_tag("%{$post_type}%", '(.+?)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&pagename=");
        } else {
            add_rewrite_tag("%{$post_type}%", '([^/]+)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&name=");
        }
        if ($args->has_archive) {
            $archive_slug = ($args->has_archive === true) ? $args->rewrite['slug'] : $args->has_archive;
            if ($args->rewrite['with_front']) {
                $archive_slug = substr($wp_rewrite->front, 1) . $archive_slug;
            } else {
                $archive_slug = $wp_rewrite->root . $archive_slug;
            }
            add_rewrite_rule("{$archive_slug}/?\$", "index.php?post_type={$post_type}", 'top');
            if ($args->rewrite['feeds'] && $wp_rewrite->feeds) {
                $feeds = '(' . trim(implode('|', $wp_rewrite->feeds)) . ')';
                add_rewrite_rule("{$archive_slug}/feed/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
                add_rewrite_rule("{$archive_slug}/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
            }
            if ($args->rewrite['pages']) {
                add_rewrite_rule("{$archive_slug}/{$wp_rewrite->pagination_base}/([0-9]{1,})/?\$", "index.php?post_type={$post_type}" . '&paged=$matches[1]', 'top');
            }
        }
        $permastruct_args = $args->rewrite;
        $permastruct_args['feed'] = $permastruct_args['feeds'];
        add_permastruct($post_type, "{$args->rewrite['slug']}/%{$post_type}%", $permastruct_args);
    }
    if ($args->register_meta_box_cb) {
        add_action('add_meta_boxes_' . $post_type, $args->register_meta_box_cb, 10, 1);
    }
    $args->labels = get_post_type_labels($args);
    $args->label = $args->labels->name;
    $wp_post_types[$post_type] = $args;
    add_action('future_' . $post_type, '_future_post_hook', 5, 2);
    foreach ($args->taxonomies as $taxonomy) {
        register_taxonomy_for_object_type($taxonomy, $post_type);
    }
    /**
     * Fires after a post type is registered.
     *
     * @since 3.3.0
     *
     * @param string $post_type Post type.
     * @param array  $args      Arguments used to register the post type.
     */
    do_action('registered_post_type', $post_type, $args);
    return $args;
}

WordPress Version: 3.8

/**
 * Register a post type. Do not use before init.
 *
 * A function for creating or modifying a post type based on the
 * parameters given. The function will accept an array (second optional
 * parameter), along with a string for the post type name.
 *
 * Optional $args contents:
 *
 * - label - Name of the post type shown in the menu. Usually plural. If not set, labels['name'] will be used.
 * - labels - An array of labels for this post type.
 *     * If not set, post labels are inherited for non-hierarchical types and page labels for hierarchical ones.
 *     * You can see accepted values in {@link get_post_type_labels()}.
 * - description - A short descriptive summary of what the post type is. Defaults to blank.
 * - public - Whether a post type is intended for use publicly either via the admin interface or by front-end users.
 *     * Defaults to false.
 *     * While the default settings of exclude_from_search, publicly_queryable, show_ui, and show_in_nav_menus are
 *       inherited from public, each does not rely on this relationship and controls a very specific intention.
 * - hierarchical - Whether the post type is hierarchical (e.g. page). Defaults to false.
 * - exclude_from_search - Whether to exclude posts with this post type from front end search results.
 *     * If not set, the opposite of public's current value is used.
 * - publicly_queryable - Whether queries can be performed on the front end for the post type as part of parse_request().
 *     * ?post_type={post_type_key}
 *     * ?{post_type_key}={single_post_slug}
 *     * ?{post_type_query_var}={single_post_slug}
 *     * If not set, the default is inherited from public.
 * - show_ui - Whether to generate a default UI for managing this post type in the admin.
 *     * If not set, the default is inherited from public.
 * - show_in_menu - Where to show the post type in the admin menu.
 *     * If true, the post type is shown in its own top level menu.
 *     * If false, no menu is shown
 *     * If a string of an existing top level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post type will
 *       be placed as a sub menu of that.
 *     * show_ui must be true.
 *     * If not set, the default is inherited from show_ui
 * - show_in_nav_menus - Makes this post type available for selection in navigation menus.
 *     * If not set, the default is inherited from public.
 * - show_in_admin_bar - Makes this post type available via the admin bar.
 *     * If not set, the default is inherited from show_in_menu
 * - menu_position - The position in the menu order the post type should appear.
 *     * show_in_menu must be true
 *     * Defaults to null, which places it at the bottom of its area.
 * - menu_icon - The url to the icon to be used for this menu. Defaults to use the posts icon.
 *     * Pass a base64-encoded SVG using a data URI, which will be colored to match the color scheme.
 *      This should begin with 'data:image/svg+xml;base64,'.
 *     * Pass the name of a Dashicons helper class to use a font icon, e.g. 'dashicons-piechart'.
 *     * Pass 'none' to leave div.wp-menu-image empty so an icon can be added via CSS.
 * - capability_type - The string to use to build the read, edit, and delete capabilities. Defaults to 'post'.
 *     * May be passed as an array to allow for alternative plurals when using this argument as a base to construct the
 *       capabilities, e.g. array('story', 'stories').
 * - capabilities - Array of capabilities for this post type.
 *     * By default the capability_type is used as a base to construct capabilities.
 *     * You can see accepted values in {@link get_post_type_capabilities()}.
 * - map_meta_cap - Whether to use the internal default meta capability handling. Defaults to false.
 * - supports - An alias for calling add_post_type_support() directly. Defaults to title and editor.
 *     * See {@link add_post_type_support()} for documentation.
 * - register_meta_box_cb - Provide a callback function that sets up the meta boxes
 *     for the edit form. Do remove_meta_box() and add_meta_box() calls in the callback.
 * - taxonomies - An array of taxonomy identifiers that will be registered for the post type.
 *     * Default is no taxonomies.
 *     * Taxonomies can be registered later with register_taxonomy() or register_taxonomy_for_object_type().
 * - has_archive - True to enable post type archives. Default is false.
 *     * Will generate the proper rewrite rules if rewrite is enabled.
 * - rewrite - Triggers the handling of rewrites for this post type. Defaults to true, using $post_type as slug.
 *     * To prevent rewrite, set to false.
 *     * To specify rewrite rules, an array can be passed with any of these keys
 *         * 'slug' => string Customize the permastruct slug. Defaults to $post_type key
 *         * 'with_front' => bool Should the permastruct be prepended with WP_Rewrite::$front. Defaults to true.
 *         * 'feeds' => bool Should a feed permastruct be built for this post type. Inherits default from has_archive.
 *         * 'pages' => bool Should the permastruct provide for pagination. Defaults to true.
 *         * 'ep_mask' => const Assign an endpoint mask.
 *             * If not specified and permalink_epmask is set, inherits from permalink_epmask.
 *             * If not specified and permalink_epmask is not set, defaults to EP_PERMALINK
 * - query_var - Sets the query_var key for this post type. Defaults to $post_type key
 *     * If false, a post type cannot be loaded at ?{query_var}={post_slug}
 *     * If specified as a string, the query ?{query_var_string}={post_slug} will be valid.
 * - can_export - Allows this post type to be exported. Defaults to true.
 * - delete_with_user - Whether to delete posts of this type when deleting a user.
 *     * If true, posts of this type belonging to the user will be moved to trash when then user is deleted.
 *     * If false, posts of this type belonging to the user will *not* be trashed or deleted.
 *     * If not set (the default), posts are trashed if post_type_supports('author'). Otherwise posts are not trashed or deleted.
 * - _builtin - true if this post type is a native or "built-in" post_type. THIS IS FOR INTERNAL USE ONLY!
 * - _edit_link - URL segement to use for edit link of this post type. THIS IS FOR INTERNAL USE ONLY!
 *
 * @since 2.9.0
 * @uses $wp_post_types Inserts new post type object into the list
 * @uses $wp_rewrite Gets default feeds
 * @uses $wp Adds query vars
 *
 * @param string $post_type Post type key, must not exceed 20 characters.
 * @param array|string $args See optional args description above.
 * @return object|WP_Error the registered post type object, or an error object.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types, $wp_rewrite, $wp;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Args prefixed with an underscore are reserved for internal use.
    $defaults = array('labels' => array(), 'description' => '', 'public' => false, 'hierarchical' => false, 'exclude_from_search' => null, 'publicly_queryable' => null, 'show_ui' => null, 'show_in_menu' => null, 'show_in_nav_menus' => null, 'show_in_admin_bar' => null, 'menu_position' => null, 'menu_icon' => null, 'capability_type' => 'post', 'capabilities' => array(), 'map_meta_cap' => null, 'supports' => array(), 'register_meta_box_cb' => null, 'taxonomies' => array(), 'has_archive' => false, 'rewrite' => true, 'query_var' => true, 'can_export' => true, 'delete_with_user' => null, '_builtin' => false, '_edit_link' => 'post.php?post=%d');
    $args = wp_parse_args($args, $defaults);
    $args = (object) $args;
    $post_type = sanitize_key($post_type);
    $args->name = $post_type;
    if (strlen($post_type) > 20) {
        return new WP_Error('post_type_too_long', __('Post types cannot exceed 20 characters in length'));
    }
    // If not set, default to the setting for public.
    if (null === $args->publicly_queryable) {
        $args->publicly_queryable = $args->public;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_ui) {
        $args->show_ui = $args->public;
    }
    // If not set, default to the setting for show_ui.
    if (null === $args->show_in_menu || !$args->show_ui) {
        $args->show_in_menu = $args->show_ui;
    }
    // If not set, default to the whether the full UI is shown.
    if (null === $args->show_in_admin_bar) {
        $args->show_in_admin_bar = true === $args->show_in_menu;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_in_nav_menus) {
        $args->show_in_nav_menus = $args->public;
    }
    // If not set, default to true if not public, false if public.
    if (null === $args->exclude_from_search) {
        $args->exclude_from_search = !$args->public;
    }
    // Back compat with quirky handling in version 3.0. #14122
    if (empty($args->capabilities) && null === $args->map_meta_cap && in_array($args->capability_type, array('post', 'page'))) {
        $args->map_meta_cap = true;
    }
    // If not set, default to false.
    if (null === $args->map_meta_cap) {
        $args->map_meta_cap = false;
    }
    $args->cap = get_post_type_capabilities($args);
    unset($args->capabilities);
    if (is_array($args->capability_type)) {
        $args->capability_type = $args->capability_type[0];
    }
    if (!empty($args->supports)) {
        add_post_type_support($post_type, $args->supports);
        unset($args->supports);
    } elseif (false !== $args->supports) {
        // Add default features
        add_post_type_support($post_type, array('title', 'editor'));
    }
    if (false !== $args->query_var && !empty($wp)) {
        if (true === $args->query_var) {
            $args->query_var = $post_type;
        } else {
            $args->query_var = sanitize_title_with_dashes($args->query_var);
        }
        $wp->add_query_var($args->query_var);
    }
    if (false !== $args->rewrite && (is_admin() || '' != get_option('permalink_structure'))) {
        if (!is_array($args->rewrite)) {
            $args->rewrite = array();
        }
        if (empty($args->rewrite['slug'])) {
            $args->rewrite['slug'] = $post_type;
        }
        if (!isset($args->rewrite['with_front'])) {
            $args->rewrite['with_front'] = true;
        }
        if (!isset($args->rewrite['pages'])) {
            $args->rewrite['pages'] = true;
        }
        if (!isset($args->rewrite['feeds']) || !$args->has_archive) {
            $args->rewrite['feeds'] = (bool) $args->has_archive;
        }
        if (!isset($args->rewrite['ep_mask'])) {
            if (isset($args->permalink_epmask)) {
                $args->rewrite['ep_mask'] = $args->permalink_epmask;
            } else {
                $args->rewrite['ep_mask'] = EP_PERMALINK;
            }
        }
        if ($args->hierarchical) {
            add_rewrite_tag("%{$post_type}%", '(.+?)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&pagename=");
        } else {
            add_rewrite_tag("%{$post_type}%", '([^/]+)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&name=");
        }
        if ($args->has_archive) {
            $archive_slug = ($args->has_archive === true) ? $args->rewrite['slug'] : $args->has_archive;
            if ($args->rewrite['with_front']) {
                $archive_slug = substr($wp_rewrite->front, 1) . $archive_slug;
            } else {
                $archive_slug = $wp_rewrite->root . $archive_slug;
            }
            add_rewrite_rule("{$archive_slug}/?\$", "index.php?post_type={$post_type}", 'top');
            if ($args->rewrite['feeds'] && $wp_rewrite->feeds) {
                $feeds = '(' . trim(implode('|', $wp_rewrite->feeds)) . ')';
                add_rewrite_rule("{$archive_slug}/feed/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
                add_rewrite_rule("{$archive_slug}/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
            }
            if ($args->rewrite['pages']) {
                add_rewrite_rule("{$archive_slug}/{$wp_rewrite->pagination_base}/([0-9]{1,})/?\$", "index.php?post_type={$post_type}" . '&paged=$matches[1]', 'top');
            }
        }
        $permastruct_args = $args->rewrite;
        $permastruct_args['feed'] = $permastruct_args['feeds'];
        add_permastruct($post_type, "{$args->rewrite['slug']}/%{$post_type}%", $permastruct_args);
    }
    if ($args->register_meta_box_cb) {
        add_action('add_meta_boxes_' . $post_type, $args->register_meta_box_cb, 10, 1);
    }
    $args->labels = get_post_type_labels($args);
    $args->label = $args->labels->name;
    $wp_post_types[$post_type] = $args;
    add_action('future_' . $post_type, '_future_post_hook', 5, 2);
    foreach ($args->taxonomies as $taxonomy) {
        register_taxonomy_for_object_type($taxonomy, $post_type);
    }
    do_action('registered_post_type', $post_type, $args);
    return $args;
}

WordPress Version: 3.7

/**
 * Register a post type. Do not use before init.
 *
 * A function for creating or modifying a post type based on the
 * parameters given. The function will accept an array (second optional
 * parameter), along with a string for the post type name.
 *
 * Optional $args contents:
 *
 * - label - Name of the post type shown in the menu. Usually plural. If not set, labels['name'] will be used.
 * - labels - An array of labels for this post type.
 *     * If not set, post labels are inherited for non-hierarchical types and page labels for hierarchical ones.
 *     * You can see accepted values in {@link get_post_type_labels()}.
 * - description - A short descriptive summary of what the post type is. Defaults to blank.
 * - public - Whether a post type is intended for use publicly either via the admin interface or by front-end users.
 *     * Defaults to false.
 *     * While the default settings of exclude_from_search, publicly_queryable, show_ui, and show_in_nav_menus are
 *       inherited from public, each does not rely on this relationship and controls a very specific intention.
 * - hierarchical - Whether the post type is hierarchical (e.g. page). Defaults to false.
 * - exclude_from_search - Whether to exclude posts with this post type from front end search results.
 *     * If not set, the opposite of public's current value is used.
 * - publicly_queryable - Whether queries can be performed on the front end for the post type as part of parse_request().
 *     * ?post_type={post_type_key}
 *     * ?{post_type_key}={single_post_slug}
 *     * ?{post_type_query_var}={single_post_slug}
 *     * If not set, the default is inherited from public.
 * - show_ui - Whether to generate a default UI for managing this post type in the admin.
 *     * If not set, the default is inherited from public.
 * - show_in_menu - Where to show the post type in the admin menu.
 *     * If true, the post type is shown in its own top level menu.
 *     * If false, no menu is shown
 *     * If a string of an existing top level menu (eg. 'tools.php' or 'edit.php?post_type=page'), the post type will
 *       be placed as a sub menu of that.
 *     * show_ui must be true.
 *     * If not set, the default is inherited from show_ui
 * - show_in_nav_menus - Makes this post type available for selection in navigation menus.
 *     * If not set, the default is inherited from public.
 * - show_in_admin_bar - Makes this post type available via the admin bar.
 *     * If not set, the default is inherited from show_in_menu
 * - menu_position - The position in the menu order the post type should appear.
 *     * show_in_menu must be true
 *     * Defaults to null, which places it at the bottom of its area.
 * - menu_icon - The url to the icon to be used for this menu. Defaults to use the posts icon.
 * - capability_type - The string to use to build the read, edit, and delete capabilities. Defaults to 'post'.
 *     * May be passed as an array to allow for alternative plurals when using this argument as a base to construct the
 *       capabilities, e.g. array('story', 'stories').
 * - capabilities - Array of capabilities for this post type.
 *     * By default the capability_type is used as a base to construct capabilities.
 *     * You can see accepted values in {@link get_post_type_capabilities()}.
 * - map_meta_cap - Whether to use the internal default meta capability handling. Defaults to false.
 * - supports - An alias for calling add_post_type_support() directly. Defaults to title and editor.
 *     * See {@link add_post_type_support()} for documentation.
 * - register_meta_box_cb - Provide a callback function that sets up the meta boxes
 *     for the edit form. Do remove_meta_box() and add_meta_box() calls in the callback.
 * - taxonomies - An array of taxonomy identifiers that will be registered for the post type.
 *     * Default is no taxonomies.
 *     * Taxonomies can be registered later with register_taxonomy() or register_taxonomy_for_object_type().
 * - has_archive - True to enable post type archives. Default is false.
 *     * Will generate the proper rewrite rules if rewrite is enabled.
 * - rewrite - Triggers the handling of rewrites for this post type. Defaults to true, using $post_type as slug.
 *     * To prevent rewrite, set to false.
 *     * To specify rewrite rules, an array can be passed with any of these keys
 *         * 'slug' => string Customize the permastruct slug. Defaults to $post_type key
 *         * 'with_front' => bool Should the permastruct be prepended with WP_Rewrite::$front. Defaults to true.
 *         * 'feeds' => bool Should a feed permastruct be built for this post type. Inherits default from has_archive.
 *         * 'pages' => bool Should the permastruct provide for pagination. Defaults to true.
 *         * 'ep_mask' => const Assign an endpoint mask.
 *             * If not specified and permalink_epmask is set, inherits from permalink_epmask.
 *             * If not specified and permalink_epmask is not set, defaults to EP_PERMALINK
 * - query_var - Sets the query_var key for this post type. Defaults to $post_type key
 *     * If false, a post type cannot be loaded at ?{query_var}={post_slug}
 *     * If specified as a string, the query ?{query_var_string}={post_slug} will be valid.
 * - can_export - Allows this post type to be exported. Defaults to true.
 * - delete_with_user - Whether to delete posts of this type when deleting a user.
 *     * If true, posts of this type belonging to the user will be moved to trash when then user is deleted.
 *     * If false, posts of this type belonging to the user will *not* be trashed or deleted.
 *     * If not set (the default), posts are trashed if post_type_supports('author'). Otherwise posts are not trashed or deleted.
 * - _builtin - true if this post type is a native or "built-in" post_type. THIS IS FOR INTERNAL USE ONLY!
 * - _edit_link - URL segement to use for edit link of this post type. THIS IS FOR INTERNAL USE ONLY!
 *
 * @since 2.9.0
 * @uses $wp_post_types Inserts new post type object into the list
 * @uses $wp_rewrite Gets default feeds
 * @uses $wp Adds query vars
 *
 * @param string $post_type Post type key, must not exceed 20 characters.
 * @param array|string $args See optional args description above.
 * @return object|WP_Error the registered post type object, or an error object.
 */
function register_post_type($post_type, $args = array())
{
    global $wp_post_types, $wp_rewrite, $wp;
    if (!is_array($wp_post_types)) {
        $wp_post_types = array();
    }
    // Args prefixed with an underscore are reserved for internal use.
    $defaults = array('labels' => array(), 'description' => '', 'public' => false, 'hierarchical' => false, 'exclude_from_search' => null, 'publicly_queryable' => null, 'show_ui' => null, 'show_in_menu' => null, 'show_in_nav_menus' => null, 'show_in_admin_bar' => null, 'menu_position' => null, 'menu_icon' => null, 'capability_type' => 'post', 'capabilities' => array(), 'map_meta_cap' => null, 'supports' => array(), 'register_meta_box_cb' => null, 'taxonomies' => array(), 'has_archive' => false, 'rewrite' => true, 'query_var' => true, 'can_export' => true, 'delete_with_user' => null, '_builtin' => false, '_edit_link' => 'post.php?post=%d');
    $args = wp_parse_args($args, $defaults);
    $args = (object) $args;
    $post_type = sanitize_key($post_type);
    $args->name = $post_type;
    if (strlen($post_type) > 20) {
        return new WP_Error('post_type_too_long', __('Post types cannot exceed 20 characters in length'));
    }
    // If not set, default to the setting for public.
    if (null === $args->publicly_queryable) {
        $args->publicly_queryable = $args->public;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_ui) {
        $args->show_ui = $args->public;
    }
    // If not set, default to the setting for show_ui.
    if (null === $args->show_in_menu || !$args->show_ui) {
        $args->show_in_menu = $args->show_ui;
    }
    // If not set, default to the whether the full UI is shown.
    if (null === $args->show_in_admin_bar) {
        $args->show_in_admin_bar = true === $args->show_in_menu;
    }
    // If not set, default to the setting for public.
    if (null === $args->show_in_nav_menus) {
        $args->show_in_nav_menus = $args->public;
    }
    // If not set, default to true if not public, false if public.
    if (null === $args->exclude_from_search) {
        $args->exclude_from_search = !$args->public;
    }
    // Back compat with quirky handling in version 3.0. #14122
    if (empty($args->capabilities) && null === $args->map_meta_cap && in_array($args->capability_type, array('post', 'page'))) {
        $args->map_meta_cap = true;
    }
    // If not set, default to false.
    if (null === $args->map_meta_cap) {
        $args->map_meta_cap = false;
    }
    $args->cap = get_post_type_capabilities($args);
    unset($args->capabilities);
    if (is_array($args->capability_type)) {
        $args->capability_type = $args->capability_type[0];
    }
    if (!empty($args->supports)) {
        add_post_type_support($post_type, $args->supports);
        unset($args->supports);
    } elseif (false !== $args->supports) {
        // Add default features
        add_post_type_support($post_type, array('title', 'editor'));
    }
    if (false !== $args->query_var && !empty($wp)) {
        if (true === $args->query_var) {
            $args->query_var = $post_type;
        } else {
            $args->query_var = sanitize_title_with_dashes($args->query_var);
        }
        $wp->add_query_var($args->query_var);
    }
    if (false !== $args->rewrite && (is_admin() || '' != get_option('permalink_structure'))) {
        if (!is_array($args->rewrite)) {
            $args->rewrite = array();
        }
        if (empty($args->rewrite['slug'])) {
            $args->rewrite['slug'] = $post_type;
        }
        if (!isset($args->rewrite['with_front'])) {
            $args->rewrite['with_front'] = true;
        }
        if (!isset($args->rewrite['pages'])) {
            $args->rewrite['pages'] = true;
        }
        if (!isset($args->rewrite['feeds']) || !$args->has_archive) {
            $args->rewrite['feeds'] = (bool) $args->has_archive;
        }
        if (!isset($args->rewrite['ep_mask'])) {
            if (isset($args->permalink_epmask)) {
                $args->rewrite['ep_mask'] = $args->permalink_epmask;
            } else {
                $args->rewrite['ep_mask'] = EP_PERMALINK;
            }
        }
        if ($args->hierarchical) {
            add_rewrite_tag("%{$post_type}%", '(.+?)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&pagename=");
        } else {
            add_rewrite_tag("%{$post_type}%", '([^/]+)', $args->query_var ? "{$args->query_var}=" : "post_type={$post_type}&name=");
        }
        if ($args->has_archive) {
            $archive_slug = ($args->has_archive === true) ? $args->rewrite['slug'] : $args->has_archive;
            if ($args->rewrite['with_front']) {
                $archive_slug = substr($wp_rewrite->front, 1) . $archive_slug;
            } else {
                $archive_slug = $wp_rewrite->root . $archive_slug;
            }
            add_rewrite_rule("{$archive_slug}/?\$", "index.php?post_type={$post_type}", 'top');
            if ($args->rewrite['feeds'] && $wp_rewrite->feeds) {
                $feeds = '(' . trim(implode('|', $wp_rewrite->feeds)) . ')';
                add_rewrite_rule("{$archive_slug}/feed/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
                add_rewrite_rule("{$archive_slug}/{$feeds}/?\$", "index.php?post_type={$post_type}" . '&feed=$matches[1]', 'top');
            }
            if ($args->rewrite['pages']) {
                add_rewrite_rule("{$archive_slug}/{$wp_rewrite->pagination_base}/([0-9]{1,})/?\$", "index.php?post_type={$post_type}" . '&paged=$matches[1]', 'top');
            }
        }
        $permastruct_args = $args->rewrite;
        $permastruct_args['feed'] = $permastruct_args['feeds'];
        add_permastruct($post_type, "{$args->rewrite['slug']}/%{$post_type}%", $permastruct_args);
    }
    if ($args->register_meta_box_cb) {
        add_action('add_meta_boxes_' . $post_type, $args->register_meta_box_cb, 10, 1);
    }
    $args->labels = get_post_type_labels($args);
    $args->label = $args->labels->name;
    $wp_post_types[$post_type] = $args;
    add_action('future_' . $post_type, '_future_post_hook', 5, 2);
    foreach ($args->taxonomies as $taxonomy) {
        register_taxonomy_for_object_type($taxonomy, $post_type);
    }
    do_action('registered_post_type', $post_type, $args);
    return $args;
}