fetch_feed( string|string[] $url ): SimplePie\SimplePie|WP_Error

804function fetch_feed( $url ) {805	if ( ! class_exists( 'SimplePie\SimplePie', false ) ) {806		require_once ABSPATH . WPINC . '/class-simplepie.php';807	}808 809	require_once ABSPATH . WPINC . '/class-wp-feed-cache-transient.php';810	require_once ABSPATH . WPINC . '/class-wp-simplepie-file.php';811	require_once ABSPATH . WPINC . '/class-wp-simplepie-sanitize-kses.php';812 813	$feed = new SimplePie\SimplePie();814 815	$feed->get_registry()->register( SimplePie\Sanitize::class, 'WP_SimplePie_Sanitize_KSES', true );816 817	/*818	 * We must manually overwrite $feed->sanitize because SimplePie's constructor819	 * sets it before we have a chance to set the sanitization class.820	 */821	$feed->sanitize = new WP_SimplePie_Sanitize_KSES();822 823	// Register the cache handler using the recommended method for SimplePie 1.3 or later.824	if ( method_exists( 'SimplePie_Cache', 'register' ) ) {825		SimplePie_Cache::register( 'wp_transient', 'WP_Feed_Cache_Transient' );826		$feed->set_cache_location( 'wp_transient' );827	} else {828		// Back-compat for SimplePie 1.2.x.829		require_once ABSPATH . WPINC . '/class-wp-feed-cache.php';830		$feed->set_cache_class( 'WP_Feed_Cache' );831	}832 833	$feed->get_registry()->register( SimplePie\File::class, 'WP_SimplePie_File', true );834 835	/** This filter is documented in wp-includes/class-wp-feed-cache-transient.php */836	$feed->set_cache_duration( apply_filters( 'wp_feed_cache_transient_lifetime', 12 * HOUR_IN_SECONDS, $url ) );837 838	/**839	 * Fires just before processing the SimplePie feed object.840	 *841	 * @since 3.0.0842	 *843	 * @param SimplePie\SimplePie $feed SimplePie feed object (passed by reference).844	 * @param string|string[]     $url  URL of feed or array of URLs of feeds to retrieve.845	 */846	do_action_ref_array( 'wp_feed_options', array( &$feed, $url ) );847 848	if ( empty( $url ) ) {849		/*850		 * @todo: Set $url to empty string once supported by SimplePie.851		 *852		 * The early return without proceeding is to work around a PHP 8.5853		 * deprecation issue resolved in https://github.com/simplepie/simplepie/pull/949854		 *855		 * To avoid the duplicate code, this block can be replaced with `$url = '';` once SimplePie856		 * is upgraded to a version that includes the fix.857		 */858		$feed->init();859		$feed->set_output_encoding( get_bloginfo( 'charset' ) );860 861		if ( $feed->error() ) {862			return new WP_Error( 'simplepie-error', $feed->error() );863		}864 865		return $feed;866	} elseif ( is_array( $url ) && count( $url ) === 1 ) {867		$url = array_shift( $url );868	} elseif ( is_array( $url ) ) {869		$feeds            = array();870		$simplepie_errors = array();871		foreach ( $url as $feed_url ) {872			$simplepie_instance = clone $feed;873			$simplepie_instance->set_feed_url( $feed_url );874			$simplepie_instance->init();875			$simplepie_instance->set_output_encoding( get_bloginfo( 'charset' ) );876 877			if ( $simplepie_instance->error() ) {878				$simplepie_errors[] = sprintf(879					/* translators: %1$s is the feed URL, %2$s is the error message. */880					__( 'Error fetching feed %1$s: %2$s' ),881					esc_url( $feed_url ),882					$simplepie_instance->error()883				);