wp_xmlrpc_server::pingback_extensions_getPingbacks( string $url )

	public function pingback_extensions_getPingbacks( $url ) {
		global $wpdb;

		/** This action is documented in wp-includes/class-wp-xmlrpc-server.php */
		do_action( 'xmlrpc_call', 'pingback.extensions.getPingbacks' );

		$url = $this->escape( $url );

		$post_ID = url_to_postid($url);
		if ( !$post_ID ) {
			// We aren't sure that the resource is available and/or pingback enabled
	  		return $this->pingback_error( 33, __( 'The specified target URL cannot be used as a target. It either doesn’t exist, or it is not a pingback-enabled resource.' ) );
		}

		$actual_post = get_post($post_ID, ARRAY_A);

		if ( !$actual_post ) {
			// No such post = resource not found
	  		return $this->pingback_error( 32, __('The specified target URL does not exist.' ) );
		}

		$comments = $wpdb->get_results( $wpdb->prepare("SELECT comment_author_url, comment_content, comment_author_IP, comment_type FROM $wpdb->comments WHERE comment_post_ID = %d", $post_ID) );

		if ( !$comments )
			return array();

		$pingbacks = array();
		foreach ( $comments as $comment ) {
			if ( 'pingback' == $comment->comment_type )
				$pingbacks[] = $comment->comment_author_url;
		}

		return $pingbacks;
	}