WordPress Version: 6.4
/**
* Balances tags of string using a modified stack.
*
* @since 2.0.4
* @since 5.3.0 Improve accuracy and add support for custom element tags.
*
* @author Leonard Lin <leonard@acm.org>
* @license GPL
* @copyright November 4, 2001
* @version 1.1
* @todo Make better - change loop condition to $text in 1.2
* @internal Modified by Scott Reilly (coffee2code) 02 Aug 2004
* 1.1 Fixed handling of append/stack pop order of end text
* Added Cleaning Hooks
* 1.0 First Version
*
* @param string $text Text to be balanced.
* @return string Balanced text.
*/
function force_balance_tags($text)
{
$tagstack = array();
$stacksize = 0;
$tagqueue = '';
$newtext = '';
// Known single-entity/self-closing tags.
$single_tags = array('area', 'base', 'basefont', 'br', 'col', 'command', 'embed', 'frame', 'hr', 'img', 'input', 'isindex', 'link', 'meta', 'param', 'source', 'track', 'wbr');
// Tags that can be immediately nested within themselves.
$nestable_tags = array('article', 'aside', 'blockquote', 'details', 'div', 'figure', 'object', 'q', 'section', 'span');
// WP bug fix for comments - in case you REALLY meant to type '< !--'.
$text = str_replace('< !--', '< !--', $text);
// WP bug fix for LOVE <3 (and other situations with '<' before a number).
$text = preg_replace('#<([0-9]{1})#', '<$1', $text);
/**
* Matches supported tags.
*
* To get the pattern as a string without the comments paste into a PHP
* REPL like `php -a`.
*
* @see https://html.spec.whatwg.org/#elements-2
* @see https://html.spec.whatwg.org/multipage/custom-elements.html#valid-custom-element-name
*
* @example
* ~# php -a
* php > $s = [paste copied contents of expression below including parentheses];
* php > echo $s;
*/
$tag_pattern = '#<' . '(/?)' . '(' . '(?:[a-z](?:[a-z0-9._]*)-(?:[a-z0-9._-]+)+)' . '|' . '(?:[\w:]+)' . ')' . '(?:' . '\s*' . '(/?)' . '|' . '(\s+)' . '([^>]*)' . ')' . '>#';
while (preg_match($tag_pattern, $text, $regex)) {
$full_match = $regex[0];
$has_leading_slash = !empty($regex[1]);
$tag_name = $regex[2];
$tag = strtolower($tag_name);
$is_single_tag = in_array($tag, $single_tags, true);
$pre_attribute_ws = isset($regex[4]) ? $regex[4] : '';
$attributes = trim(isset($regex[5]) ? $regex[5] : $regex[3]);
$has_self_closer = str_ends_with($attributes, '/');
$newtext .= $tagqueue;
$i = strpos($text, $full_match);
$l = strlen($full_match);
// Clear the shifter.
$tagqueue = '';
if ($has_leading_slash) {
// End tag.
// If too many closing tags.
if ($stacksize <= 0) {
$tag = '';
// Or close to be safe $tag = '/' . $tag.
// If stacktop value = tag close value, then pop.
} elseif ($tagstack[$stacksize - 1] === $tag) {
// Found closing tag.
$tag = '</' . $tag . '>';
// Close tag.
array_pop($tagstack);
--$stacksize;
} else {
// Closing tag not at top, search for it.
for ($j = $stacksize - 1; $j >= 0; $j--) {
if ($tagstack[$j] === $tag) {
// Add tag to tagqueue.
for ($k = $stacksize - 1; $k >= $j; $k--) {
$tagqueue .= '</' . array_pop($tagstack) . '>';
--$stacksize;
}
break;
}
}
$tag = '';
}
} else {
// Begin tag.
if ($has_self_closer) {
/*
* If it presents itself as a self-closing tag, but it isn't a known single-entity self-closing tag,
* then don't let it be treated as such and immediately close it with a closing tag.
* The tag will encapsulate no text as a result.
*/
if (!$is_single_tag) {
$attributes = trim(substr($attributes, 0, -1)) . "></{$tag}";
}
} elseif ($is_single_tag) {
// Else if it's a known single-entity tag but it doesn't close itself, do so.
$pre_attribute_ws = ' ';
$attributes .= '/';
} else {
/*
* It's not a single-entity tag.
* If the top of the stack is the same as the tag we want to push, close previous tag.
*/
if ($stacksize > 0 && !in_array($tag, $nestable_tags, true) && $tagstack[$stacksize - 1] === $tag) {
$tagqueue = '</' . array_pop($tagstack) . '>';
--$stacksize;
}
$stacksize = array_push($tagstack, $tag);
}
// Attributes.
if ($has_self_closer && $is_single_tag) {
// We need some space - avoid <br/> and prefer <br />.
$pre_attribute_ws = ' ';
}
$tag = '<' . $tag . $pre_attribute_ws . $attributes . '>';
// If already queuing a close tag, then put this tag on too.
if (!empty($tagqueue)) {
$tagqueue .= $tag;
$tag = '';
}
}
$newtext .= substr($text, 0, $i) . $tag;
$text = substr($text, $i + $l);
}
// Clear tag queue.
$newtext .= $tagqueue;
// Add remaining text.
$newtext .= $text;
while ($x = array_pop($tagstack)) {
$newtext .= '</' . $x . '>';
// Add remaining tags to close.
}
// WP fix for the bug with HTML comments.
$newtext = str_replace('< !--', '<!--', $newtext);
$newtext = str_replace('< !--', '< !--', $newtext);
return $newtext;
}