trackback

		if ( '' !== $service ) {
			weblog_ping( $service );
		}
	}

	return $post_id;
}

/**
 * Pings back the links found in a post.
 *
 * @since 0.71
 * @since 4.7.0 `$post_id` can be a WP_Post object.
 *
 * @param string      $content Post content to check for links. If empty will retrieve from post.
 * @param int|WP_Post $post_id Post Object or ID.
 */
function pingback( $content, $post_id ) {
	include_once ABSPATH . WPINC . '/class-IXR.php';
	include_once ABSPATH . WPINC . '/class-wp-http-ixr-client.php';

	// Original code by Mort (http://mort.mine.nu:8080).
	$post_links = array();

	$post = get_post( $post_id );