/htdocs/wp-includes/class-wp-embed.php

<?php
/**
 * API for easily embedding rich media such as videos and images into content.
 *
 * @package WordPress
 * @subpackage Embed
 * @since 2.9.0
 */
class WP_Embed {
	var $handlers = array();
	var $post_ID;
	var $usecache = true;
	var $linkifunknown = true;

	/**
	 * Constructor
	 */
	function __construct() {
		// Hack to get the [embed] shortcode to run before wpautop()
		add_filter( 'the_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 );

		// When a post is saved, invalidate the oEmbed cache
		add_action( 'pre_post_update', array( $this, 'delete_oembed_caches' ) );

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

	/**
	 * Process 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 {@link do_shortcode()}, and then re-registers the old shortcodes.
	 *
	 * @uses $shortcode_tags
	 * @uses remove_all_shortcodes()
	 * @uses add_shortcode()
	 * @uses do_shortcode()
	 *
	 * @param string $content Content to parse
	 * @return string Content with shortcode parsed
	 */
	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 );

		// 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().
	 */
	function maybe_run_ajax_cache() {
		$post = get_post();

		if ( ! $post || empty($_GET['message']) || 1 != $_GET['message'] )
			return;

?>
<script type="text/javascript">
/* <![CDATA[ */
	jQuery(document).ready(function($){
		$.get("<?php echo admin_url( 'admin-ajax.php?action=oembed-cache&post=' . $post->ID, 'relative' ); ?>");
	});
/* ]]> */
</script>
<?php
	}

	/**
	 * Register an embed handler. Do not use this function directly, use {@link 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 callback $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 (default: 10). 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.
	 */
	function register_handler( $id, $regex, $callback, $priority = 10 ) {
		$this->handlers[$priority][$id] = array(
			'regex'    => $regex,
			'callback' => $callback,
		);
	}

	/**
	 * Unregister a previously registered embed handler. Do not use this function directly, use {@link 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).
	 */
	function unregister_handler( $id, $priority = 10 ) {
		if ( isset($this->handlers[$priority][$id]) )
			unset($this->handlers[$priority][$id]);
	}

	/**
	 * The {@link 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 {@link WP_oEmbed} class.
	 *
	 * @uses wp_oembed_get()
	 * @uses wp_parse_args()
	 * @uses wp_embed_defaults()
	 * @uses WP_Embed::maybe_make_link()
	 * @uses get_option()
	 * @uses author_can()
	 * @uses wp_cache_get()
	 * @uses wp_cache_set()
	 * @uses get_post_meta()
	 * @uses update_post_meta()
	 *
	 * @param array $attr Shortcode attributes.
	 * @param string $url The URL attempting to be embedded.
	 * @return string The embed HTML on success, otherwise the original URL.
	 */
	function shortcode( $attr, $url = '' ) {
		$post = get_post();

		if ( empty( $url ) )
			return '';

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

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

		// Look for known internal handlers
		ksort( $this->handlers );
		foreach ( $this->handlers as $priority => $handlers ) {
			foreach ( $handlers as $id => $handler ) {
				if ( preg_match( $handler['regex'], $url, $matches ) && is_callable( $handler['callback'] ) ) {
					if ( false !== $return = call_user_func( $handler['callback'], $matches, $attr, $url, $rawattr ) )
						return apply_filters( 'embed_handler_html', $return, $url, $attr );
				}
			}
		}

		$post_ID = ( ! empty( $post->ID ) ) ? $post->ID : null;
		if ( ! empty( $this->post_ID ) ) // Potentially set by WP_Embed::cache_oembed()
			$post_ID = $this->post_ID;

		// Unknown URL format. Let oEmbed have a go.
		if ( $post_ID ) {

			// Check for a cached result (stored in the post meta)
			$cachekey = '_oembed_' . md5( $url . serialize( $attr ) );
			if ( $this->usecache ) {
				$cache = get_post_meta( $post_ID, $cachekey, true );

				// Failures are cached
				if ( '{{unknown}}' === $cache )
					return $this->maybe_make_link( $url );

				if ( ! empty( $cache ) )
					return apply_filters( 'embed_oembed_html', $cache, $url, $attr, $post_ID );
			}

			// Use oEmbed to get the HTML
			$attr['discover'] = ( apply_filters('embed_oembed_discover', false) && author_can( $post_ID, 'unfiltered_html' ) );
			$html = wp_oembed_get( $url, $attr );

			// Cache the result
			$cache = ( $html ) ? $html : '{{unknown}}';
			update_post_meta( $post_ID, $cachekey, $cache );

			// If there was a result, return it
			if ( $html )
				return apply_filters( 'embed_oembed_html', $html, $url, $attr, $post_ID );
		}

		// Still unknown
		return $this->maybe_make_link( $url );
	}

	/**
	 * Delete all oEmbed caches.
	 *
	 * @param int $post_ID Post ID to delete the caches for.
	 */
	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 ( '_oembed_' == substr( $post_meta_key, 0, 8 ) )
				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.
	 */
	function cache_oembed( $post_ID ) {
		$post = get_post( $post_ID );

		if ( empty($post->ID) || !in_array( $post->post_type, apply_filters( 'embed_cache_oembed_types', array( 'post', 'page' ) ) ) )
			return;

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

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

			$this->usecache = true;
		}
	}

	/**
	 * Passes any unlinked URLs that are on their own line to {@link WP_Embed::shortcode()} for potential embedding.
	 *
	 * @uses WP_Embed::autoembed_callback()
	 *
	 * @param string $content The content to be searched.
	 * @return string Potentially modified $content.
	 */
	function autoembed( $content ) {
		return preg_replace_callback( '|^\s*(https?://[^\s"]+)\s*$|im', array( $this, 'autoembed_callback' ), $content );
	}

	/**
	 * Callback function for {@link WP_Embed::autoembed()}.
	 *
	 * @uses WP_Embed::shortcode()
	 *
	 * @param array $match A regex match array.
	 * @return string The embed HTML on success, otherwise the original URL.
	 */
	function autoembed_callback( $match ) {
		$oldval = $this->linkifunknown;
		$this->linkifunknown = false;
		$return = $this->shortcode( array(), $match[1] );
		$this->linkifunknown = $oldval;

		return "\n$return\n";
	}

	/**
	 * Conditionally makes a hyperlink based on an internal class variable.
	 *
	 * @param string $url URL to potentially be linked.
	 * @return string Linked URL or the original URL.
	 */
	function maybe_make_link( $url ) {
		$output = ( $this->linkifunknown ) ? '<a href="' . esc_url($url) . '">' . esc_html($url) . '</a>' : $url;
		return apply_filters( 'embed_maybe_make_link', $output, $url );
	}
}
$GLOBALS['wp_embed'] = new WP_Embed();