discover_pingback_server_uri example

    do_action_ref_array( 'pre_ping', array( &$post_links, &$pung, $post->ID ) );

    foreach ( (array) $post_links as $pagelinkedto ) {
        $pingback_server_url = discover_pingback_server_uri( $pagelinkedto );

        if ( $pingback_server_url ) {
            if ( function_exists( 'set_time_limit' ) ) {
                set_time_limit( 60 );
            }

            // Now, the RPC call.             $pagelinkedfrom = get_permalink( $post );

            // Using a timeout of 3 seconds should be enough to cover slow servers.             $client          = new WP_HTTP_IXR_Client( $pingback_server_url );