WordPress Version: 5.4
/**
* Allow subdomain installation
*
* @since 3.0.0
* @return bool Whether subdomain installation is allowed
*/
function allow_subdomain_install()
{
$domain = preg_replace('|https?://([^/]+)|', '$1', get_option('home'));
if (parse_url(get_option('home'), PHP_URL_PATH) || 'localhost' === $domain || preg_match('|^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$|', $domain)) {
return false;
}
return true;
}