Filter hook 'http_headers_useragent'

Description

Filters the pingback source URI.

Occurrences

Parameters

PHP Doc

/**
		 * Filters the pingback source URI.
		 *
		 * @since 3.6.0
		 *
		 * @param string $pagelinkedfrom URI of the page linked from.
		 * @param string $pagelinkedto   URI of the page linked to.
		 */
		$pagelinkedfrom = apply_filters( 'pingback_ping_source_uri', $pagelinkedfrom, $pagelinkedto );

		if ( ! $pagelinkedfrom ) {
			return $this->pingback_error( 0, __( 'A valid URL was not provided.' ) );
		}

		// Check if the page linked to is on our site.
		$pos1 = strpos( $pagelinkedto, str_replace( array( 'http://www.', 'http://', 'https://www.', 'https://' ), '', get_option( 'home' ) ) );
		if ( ! $pos1 ) {
			return $this->pingback_error( 0, __( 'Is there no link to us?' ) );
		}

		/*
		 * Let's find which post is linked to.
		 * FIXME: Does url_to_postid() cover all these cases already?
		 * If so, then let's use it and drop the old code.
		 */
		$urltest = parse_url( $pagelinkedto );
		$post_id = url_to_postid( $pagelinkedto );
		if ( $post_id ) {
			// $way
		} elseif ( isset( $urltest['path'] ) && preg_match( '#p/[0-9]{1,}#', $urltest['path'], $match ) ) {
			// The path defines the post_ID (archives/p/XXXX).
			$blah    = explode( '/', $match[0] );
			$post_id = (int) $blah[1];
		} elseif ( isset( $urltest['query'] ) && preg_match( '#p=[0-9]{1,}#', $urltest['query'], $match ) ) {
			// The query string defines the post_ID (?p=XXXX).
			$blah    = explode( '=', $match[0] );
			$post_id = (int) $blah[1];
		} elseif ( isset( $urltest['fragment'] ) ) {
			// An #anchor is there, it's either...
			if ( (int) $urltest['fragment'] ) {
				// ...an integer #XXXX (simplest case),
				$post_id = (int) $urltest['fragment'];
			} elseif ( preg_match( '/post-[0-9]+/', $urltest['fragment'] ) ) {
				// ...a post ID in the form 'post-###',
				$post_id = preg_replace( '/[^0-9]+/', '', $urltest['fragment'] );
			} elseif ( is_string( $urltest['fragment'] ) ) {
				// ...or a string #title, a little more complicated.
				$title   = preg_replace( '/[^a-z0-9]/i', '.', $urltest['fragment'] );
				$sql     = $wpdb->prepare( "SELECT ID FROM $wpdb->posts WHERE post_title RLIKE %s", $title );
				$post_id = $wpdb->get_var( $sql );
				if ( ! $post_id ) {
					// Returning unknown error '0' is better than die()'ing.
					return $this->pingback_error( 0, '' );
				}
			}
		} else {
			// TODO: Attempt to extract a post ID from the given URL.
			return $this->pingback_error( 33, __( 'The specified target URL cannot be used as a target. It either does not exist, or it is not a pingback-enabled resource.' ) );
		}
		$post_id = (int) $post_id;

		$post = get_post( $post_id );

		if ( ! $post ) { // Post not found.
			return $this->pingback_error( 33, __( 'The specified target URL cannot be used as a target. It either does not exist, or it is not a pingback-enabled resource.' ) );
		}

		if ( url_to_postid( $pagelinkedfrom ) == $post_id ) {
			return $this->pingback_error( 0, __( 'The source URL and the target URL cannot both point to the same resource.' ) );
		}

		// Check if pings are on.
		if ( ! pings_open( $post ) ) {
			return $this->pingback_error( 33, __( 'The specified target URL cannot be used as a target. It either does not exist, or it is not a pingback-enabled resource.' ) );
		}

		// Let's check that the remote site didn't already pingback this entry.
		if ( $wpdb->get_results( $wpdb->prepare( "SELECT * FROM $wpdb->comments WHERE comment_post_ID = %d AND comment_author_url = %s", $post_id, $pagelinkedfrom ) ) ) {
			return $this->pingback_error( 48, __( 'The pingback has already been registered.' ) );
		}

		/*
		 * The remote site may have sent the pingback before it finished publishing its own content
		 * containing this pingback URL. If that happens then it won't be immediately possible to fetch
		 * the pinging post; adding a small delay reduces the likelihood of this happening.
		 *
		 * While there are more robust methods than calling `sleep()` here (because `sleep()` merely
		 * mitigates the risk of requesting the remote post before it's available), this is effective
		 * enough for most cases and avoids introducing more complexity into this code.
		 *
		 * One way to improve the reliability of this code might be to add failure-handling to the remote
		 * fetch and retry up to a set number of times if it receives a 404. This could also handle 401 and
		 * 403 responses to differentiate the "does not exist" failure from the "may not access" failure.
		 */