<form method="POST">
    <h3>Editing: class-wp-embed.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php
/**
 * API for easily embedding rich media such as videos and images into content.
 *
 * @package WordPress
 * @subpackage Embed
 * @since 2.9.0
 */
#[AllowDynamicProperties]
class WP_Embed {
	public $handlers = array();
	public $post_ID;
	public $usecache      = true;
	public $linkifunknown = true;
	public $last_attr     = array();
	public $last_url      = '';

	/**
	 * When a URL cannot be embedded, return false instead of returning a link
	 * or the URL.
	 *
	 * Bypasses the {@see 'embed_maybe_make_link'} filter.
	 *
	 * @var bool
	 */
	public $return_false_on_fail = false;

	/**
	 * Constructor
	 */
	public function __construct() {
		// Hack to get the [embed] shortcode to run before wpautop().
		add_filter( 'the_content', array( $this, 'run_shortcode' ), 8 );
		add_filter( 'widget_text_content', array( $this, 'run_shortcode' ), 8 );
		add_filter( 'widget_block_content', array( $this, 'run_shortcode' ), 8 );

		// Shortcode placeholder for strip_shortcodes().
		add_shortcode( 'embed', '__return_false' );

		// Attempts to embed all URLs in a post.
		add_filter( 'the_content', array( $this, 'autoembed' ), 8 );
		add_filter( 'widget_text_content', array( $this, 'autoembed' ), 8 );
		add_filter( 'widget_block_content', array( $this, 'autoembed' ), 8 );

		// After a post is saved, cache oEmbed items via Ajax.
		add_action( 'edit_form_advanced', array( $this, 'maybe_run_ajax_cache' ) );
		add_action( 'edit_page_form', array( $this, 'maybe_run_ajax_cache' ) );
	}

	/**
	 * Processes the [embed] shortcode.
	 *
	 * Since the [embed] shortcode needs to be run earlier than other shortcodes,
	 * this function removes all existing shortcodes, registers the [embed] shortcode,
	 * calls do_shortcode(), and then re-registers the old shortcodes.
	 *
	 * @global array $shortcode_tags
	 *
	 * @param string $content Content to parse.
	 * @return string Content with shortcode parsed.
	 */
	public function run_shortcode( $content ) {
		global $shortcode_tags;

		// Back up current registered shortcodes and clear them all out.
		$orig_shortcode_tags = $shortcode_tags;
		remove_all_shortcodes();

		add_shortcode( 'embed', array( $this, 'shortcode' ) );

		// Do the shortcode (only the [embed] one is registered).
		$content = do_shortcode( $content, true );

		// Put the original shortcodes back.
		$shortcode_tags = $orig_shortcode_tags;

		return $content;
	}

	/**
	 * If a post/page was saved, then output JavaScript to make
	 * an Ajax request that will call WP_Embed::cache_oembed().
	 */
	public function maybe_run_ajax_cache() {
		$post = get_post();

		if ( ! $post || empty( $_GET['message'] ) ) {
			return;
		}
		?&gt;
&lt;script type=&quot;text/javascript&quot;&gt;
	jQuery( function($) {
		$.get(&quot;&lt;?php echo esc_url( admin_url( 'admin-ajax.php', 'relative' ) ) . '?action=oembed-cache&amp;post=' . $post-&gt;ID; ?&gt;&quot;);
	} );
&lt;/script&gt;
		&lt;?php
	}

	/**
	 * Registers an embed handler.
	 *
	 * Do not use this function directly, use wp_embed_register_handler() instead.
	 *
	 * This function should probably also only be used for sites that do not support oEmbed.
	 *
	 * @param string   $id       An internal ID/name for the handler. Needs to be unique.
	 * @param string   $regex    The regex that will be used to see if this handler should be used for a URL.
	 * @param callable $callback The callback function that will be called if the regex is matched.
	 * @param int      $priority Optional. Used to specify the order in which the registered handlers will be tested.
	 *                           Lower numbers correspond with earlier testing, and handlers with the same priority are
	 *                           tested in the order in which they were added to the action. Default 10.
	 */
	public function register_handler( $id, $regex, $callback, $priority = 10 ) {
		$this-&gt;handlers[ $priority ][ $id ] = array(
			'regex'    =&gt; $regex,
			'callback' =&gt; $callback,
		);
	}

	/**
	 * Unregisters a previously-registered embed handler.
	 *
	 * Do not use this function directly, use wp_embed_unregister_handler() instead.
	 *
	 * @param string $id       The handler ID that should be removed.
	 * @param int    $priority Optional. The priority of the handler to be removed (default: 10).
	 */
	public function unregister_handler( $id, $priority = 10 ) {
		unset( $this-&gt;handlers[ $priority ][ $id ] );
	}

	/**
	 * Returns embed HTML for a given URL from embed handlers.
	 *
	 * Attempts to convert a URL into embed HTML by checking the URL
	 * against the regex of the registered embed handlers.
	 *
	 * @since 5.5.0
	 *
	 * @param array  $attr {
	 *     Shortcode attributes. Optional.
	 *
	 *     @type int $width  Width of the embed in pixels.
	 *     @type int $height Height of the embed in pixels.
	 * }
	 * @param string $url The URL attempting to be embedded.
	 * @return string|false The embed HTML on success, false otherwise.
	 */
	public function get_embed_handler_html( $attr, $url ) {
		$rawattr = $attr;
		$attr    = wp_parse_args( $attr, wp_embed_defaults( $url ) );

		ksort( $this-&gt;handlers );
		foreach ( $this-&gt;handlers as $priority =&gt; $handlers ) {
			foreach ( $handlers as $id =&gt; $handler ) {
				if ( preg_match( $handler['regex'], $url, $matches ) &amp;&amp; is_callable( $handler['callback'] ) ) {
					$return = call_user_func( $handler['callback'], $matches, $attr, $url, $rawattr );
					if ( false !== $return ) {
						/**
						 * Filters the returned embed HTML.
						 *
						 * @since 2.9.0
						 *
						 * @see WP_Embed::shortcode()
						 *
						 * @param string $return The HTML result of the shortcode.
						 * @param string $url    The embed URL.
						 * @param array  $attr   An array of shortcode attributes.
						 */
						return apply_filters( 'embed_handler_html', $return, $url, $attr );
					}
				}
			}
		}

		return false;
	}

	/**
	 * The do_shortcode() callback function.
	 *
	 * Attempts to convert a URL into embed HTML. Starts by checking the URL against the regex of
	 * the registered embed handlers. If none of the regex matches and it's enabled, then the URL
	 * will be given to the WP_oEmbed class.
	 *
	 * @param array  $attr {
	 *     Shortcode attributes. Optional.
	 *
	 *     @type int $width  Width of the embed in pixels.
	 *     @type int $height Height of the embed in pixels.
	 * }
	 * @param string $url The URL attempting to be embedded.
	 * @return string|false The embed HTML on success, otherwise the original URL.
	 *                      `-&gt;maybe_make_link()` can return false on failure.
	 */
	public function shortcode( $attr, $url = '' ) {
		$post = get_post();

		if ( empty( $url ) &amp;&amp; ! empty( $attr['src'] ) ) {
			$url = $attr['src'];
		}

		$this-&gt;last_url = $url;

		if ( empty( $url ) ) {
			$this-&gt;last_attr = $attr;
			return '';
		}

		$rawattr = $attr;
		$attr    = wp_parse_args( $attr, wp_embed_defaults( $url ) );

		$this-&gt;last_attr = $attr;

		/*
		 * KSES converts &amp; into &amp;amp; and we need to undo this.
		 * See https://core.trac.wordpress.org/ticket/11311
		 */
		$url = str_replace( '&amp;amp;', '&amp;', $url );

		// Look for known internal handlers.
		$embed_handler_html = $this-&gt;get_embed_handler_html( $rawattr, $url );
		if ( false !== $embed_handler_html ) {
			return $embed_handler_html;
		}

		$post_id = ( ! empty( $post-&gt;ID ) ) ? $post-&gt;ID : null;

		// Potentially set by WP_Embed::cache_oembed().
		if ( ! empty( $this-&gt;post_ID ) ) {
			$post_id = $this-&gt;post_ID;
		}

		// Check for a cached result (stored as custom post or in the post meta).
		$key_suffix    = md5( $url . serialize( $attr ) );
		$cachekey      = '_oembed_' . $key_suffix;
		$cachekey_time = '_oembed_time_' . $key_suffix;

		/**
		 * Filters the oEmbed TTL value (time to live).
		 *
		 * @since 4.0.0
		 *
		 * @param int    $time    Time to live (in seconds).
		 * @param string $url     The attempted embed URL.
		 * @param array  $attr    An array of shortcode attributes.
		 * @param int    $post_id Post ID.
		 */
		$ttl = apply_filters( 'oembed_ttl', DAY_IN_SECONDS, $url, $attr, $post_id );

		$cache      = '';
		$cache_time = 0;

		$cached_post_id = $this-&gt;find_oembed_post_id( $key_suffix );

		if ( $post_id ) {
			$cache      = get_post_meta( $post_id, $cachekey, true );
			$cache_time = get_post_meta( $post_id, $cachekey_time, true );

			if ( ! $cache_time ) {
				$cache_time = 0;
			}
		} elseif ( $cached_post_id ) {
			$cached_post = get_post( $cached_post_id );

			$cache      = $cached_post-&gt;post_content;
			$cache_time = strtotime( $cached_post-&gt;post_modified_gmt );
		}

		$cached_recently = ( time() - $cache_time ) &lt; $ttl;

		if ( $this-&gt;usecache || $cached_recently ) {
			// Failures are cached. Serve one if we're using the cache.
			if ( '{{unknown}}' === $cache ) {
				return $this-&gt;maybe_make_link( $url );
			}

			if ( ! empty( $cache ) ) {
				/**
				 * Filters the cached oEmbed HTML.
				 *
				 * @since 2.9.0
				 *
				 * @see WP_Embed::shortcode()
				 *
				 * @param string $cache   The cached HTML result, stored in post meta.
				 * @param string $url     The attempted embed URL.
				 * @param array  $attr    An array of shortcode attributes.
				 * @param int    $post_id Post ID.
				 */
				return apply_filters( 'embed_oembed_html', $cache, $url, $attr, $post_id );
			}
		}

		/**
		 * Filters whether to inspect the given URL for discoverable link tags.
		 *
		 * @since 2.9.0
		 * @since 4.4.0 The default value changed to true.
		 *
		 * @see WP_oEmbed::discover()
		 *
		 * @param bool $enable Whether to enable `&lt;link&gt;` tag discovery. Default true.
		 */
		$attr['discover'] = apply_filters( 'embed_oembed_discover', true );

		// Use oEmbed to get the HTML.
		$html = wp_oembed_get( $url, $attr );

		if ( $post_id ) {
			if ( $html ) {
				update_post_meta( $post_id, $cachekey, $html );
				update_post_meta( $post_id, $cachekey_time, time() );
			} elseif ( ! $cache ) {
				update_post_meta( $post_id, $cachekey, '{{unknown}}' );
			}
		} else {
			$has_kses = false !== has_filter( 'content_save_pre', 'wp_filter_post_kses' );

			if ( $has_kses ) {
				// Prevent KSES from corrupting JSON in post_content.
				kses_remove_filters();
			}

			$insert_post_args = array(
				'post_name'   =&gt; $key_suffix,
				'post_status' =&gt; 'publish',
				'post_type'   =&gt; 'oembed_cache',
			);

			if ( $html ) {
				if ( $cached_post_id ) {
					wp_update_post(
						wp_slash(
							array(
								'ID'           =&gt; $cached_post_id,
								'post_content' =&gt; $html,
							)
						)
					);
				} else {
					wp_insert_post(
						wp_slash(
							array_merge(
								$insert_post_args,
								array(
									'post_content' =&gt; $html,
								)
							)
						)
					);
				}
			} elseif ( ! $cache ) {
				wp_insert_post(
					wp_slash(
						array_merge(
							$insert_post_args,
							array(
								'post_content' =&gt; '{{unknown}}',
							)
						)
					)
				);
			}

			if ( $has_kses ) {
				kses_init_filters();
			}
		}

		// If there was a result, return it.
		if ( $html ) {
			/** This filter is documented in wp-includes/class-wp-embed.php */
			return apply_filters( 'embed_oembed_html', $html, $url, $attr, $post_id );
		}

		// Still unknown.
		return $this-&gt;maybe_make_link( $url );
	}

	/**
	 * Deletes all oEmbed caches. Unused by core as of 4.0.0.
	 *
	 * @param int $post_id Post ID to delete the caches for.
	 */
	public function delete_oembed_caches( $post_id ) {
		$post_metas = get_post_custom_keys( $post_id );
		if ( empty( $post_metas ) ) {
			return;
		}

		foreach ( $post_metas as $post_meta_key ) {
			if ( str_starts_with( $post_meta_key, '_oembed_' ) ) {
				delete_post_meta( $post_id, $post_meta_key );
			}
		}
	}

	/**
	 * Triggers a caching of all oEmbed results.
	 *
	 * @param int $post_id Post ID to do the caching for.
	 */
	public function cache_oembed( $post_id ) {
		$post = get_post( $post_id );

		$post_types = get_post_types( array( 'show_ui' =&gt; true ) );

		/**
		 * Filters the array of post types to cache oEmbed results for.
		 *
		 * @since 2.9.0
		 *
		 * @param string[] $post_types Array of post type names to cache oEmbed results for. Defaults to post types with `show_ui` set to true.
		 */
		$cache_oembed_types = apply_filters( 'embed_cache_oembed_types', $post_types );

		if ( empty( $post-&gt;ID ) || ! in_array( $post-&gt;post_type, $cache_oembed_types, true ) ) {
			return;
		}

		// Trigger a caching.
		if ( ! empty( $post-&gt;post_content ) ) {
			$this-&gt;post_ID  = $post-&gt;ID;
			$this-&gt;usecache = false;

			$content = $this-&gt;run_shortcode( $post-&gt;post_content );
			$this-&gt;autoembed( $content );

			$this-&gt;usecache = true;
		}
	}

	/**
	 * Passes any unlinked URLs that are on their own line to WP_Embed::shortcode() for potential embedding.
	 *
	 * @see WP_Embed::autoembed_callback()
	 *
	 * @param string $content The content to be searched.
	 * @return string Potentially modified $content.
	 */
	public function autoembed( $content ) {
		// Replace line breaks from all HTML elements with placeholders.
		$content = wp_replace_in_html_tags( $content, array( &quot;\n&quot; =&gt; '&lt;!-- wp-line-break --&gt;' ) );

		if ( preg_match( '#(^|\s|&gt;)https?://#i', $content ) ) {
			// Find URLs on their own line.
			$content = preg_replace_callback( '|^(\s*)(https?://[^\s&lt;&gt;&quot;]+)(\s*)$|im', array( $this, 'autoembed_callback' ), $content );
			// Find URLs in their own paragraph.
			$content = preg_replace_callback( '|(&lt;p(?: [^&gt;]*)?&gt;\s*)(https?://[^\s&lt;&gt;&quot;]+)(\s*&lt;\/p&gt;)|i', array( $this, 'autoembed_callback' ), $content );
		}

		// Put the line breaks back.
		return str_replace( '&lt;!-- wp-line-break --&gt;', &quot;\n&quot;, $content );
	}

	/**
	 * Callback function for WP_Embed::autoembed().
	 *
	 * @param array $matches A regex match array.
	 * @return string The embed HTML on success, otherwise the original URL.
	 */
	public function autoembed_callback( $matches ) {
		$oldval              = $this-&gt;linkifunknown;
		$this-&gt;linkifunknown = false;
		$return              = $this-&gt;shortcode( array(), $matches[2] );
		$this-&gt;linkifunknown = $oldval;

		return $matches[1] . $return . $matches[3];
	}

	/**
	 * Conditionally makes a hyperlink based on an internal class variable.
	 *
	 * @param string $url URL to potentially be linked.
	 * @return string|false Linked URL or the original URL. False if 'return_false_on_fail' is true.
	 */
	public function maybe_make_link( $url ) {
		if ( $this-&gt;return_false_on_fail ) {
			return false;
		}

		$output = ( $this-&gt;linkifunknown ) ? '&lt;a href=&quot;' . esc_url( $url ) . '&quot;&gt;' . esc_html( $url ) . '&lt;/a&gt;' : $url;

		/**
		 * Filters the returned, maybe-linked embed URL.
		 *
		 * @since 2.9.0
		 *
		 * @param string $output The linked or original URL.
		 * @param string $url    The original URL.
		 */
		return apply_filters( 'embed_maybe_make_link', $output, $url );
	}

	/**
	 * Finds the oEmbed cache post ID for a given cache key.
	 *
	 * @since 4.9.0
	 *
	 * @param string $cache_key oEmbed cache key.
	 * @return int|null Post ID on success, null on failure.
	 */
	public function find_oembed_post_id( $cache_key ) {
		$cache_group    = 'oembed_cache_post';
		$oembed_post_id = wp_cache_get( $cache_key, $cache_group );

		if ( $oembed_post_id &amp;&amp; 'oembed_cache' === get_post_type( $oembed_post_id ) ) {
			return $oembed_post_id;
		}

		$oembed_post_query = new WP_Query(
			array(
				'post_type'              =&gt; 'oembed_cache',
				'post_status'            =&gt; 'publish',
				'name'                   =&gt; $cache_key,
				'posts_per_page'         =&gt; 1,
				'no_found_rows'          =&gt; true,
				'cache_results'          =&gt; true,
				'update_post_meta_cache' =&gt; false,
				'update_post_term_cache' =&gt; false,
				'lazy_load_term_meta'    =&gt; false,
			)
		);

		if ( ! empty( $oembed_post_query-&gt;posts ) ) {
			// Note: 'fields' =&gt; 'ids' is not being used in order to cache the post object as it will be needed.
			$oembed_post_id = $oembed_post_query-&gt;posts[0]-&gt;ID;
			wp_cache_set( $cache_key, $oembed_post_id, $cache_group );

			return $oembed_post_id;
		}

		return null;
	}
}
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