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

Compatibility

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$urlstring|string[]

URL of feed to retrieve. If an array of URLs, the feeds are merged using SimplePie's multifeed feature.
See also http://simplepie.org/wiki/faq/typical_multifeed_gotchas

Return value

SimplePie\SimplePie|WP_Error

SimplePie object on success or WP_Error object on failure.

Performance profile

How much work a call to fetch_feed() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.

Cost class

Heavy

Reads stored settings via get_option(), cached per request but not free on a cold cache.

Scaling

Scales with input

The body loops, so the work grows with what you pass in.

Instructions

82–106

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 194.

Plugin surface

2 hooks

Third-party callbacks on 'wp_feed_cache_transient_lifetime', 'wp_feed_options' run inside this call, and their cost is not bounded by anything here.

Called by

6

6 places in core call this, so the cost is paid more often than your own code shows.

What it touches

• hookthird-party callbacksapply_filters()called directly
• optionoption read or writeget_option()one call below fetch_feed()

Further down the call graph this can also reach cache, serialize, query and transient. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.

What one call costs · 16 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost fetch_feed() can have, taken from its control-flow graph on PHP 8.5.

Hooks and filters fired · 2

2 hooks fire while fetch_feed() runs, in this order:

1. 1
   apply_filters( wp_feed_cache_transient_lifetime )filterline 836 (+32 into the body)

   Filters the transient lifetime of the feed cache.

2. 2
   do_action( wp_feed_options )actionline 846 (+42 into the body)

   Fires just before processing the SimplePie feed object.

Uses · 10

• apply_filters()Calls the callback functions that have been added to a filter hook.
• do_action_ref_array()Calls the callback functions that have been added to an action hook, specifying arguments in an array.
• get_bloginfo()Retrieves information about the current site.
• __()Retrieves the translation of $text.
• esc_url()Checks and cleans a URL.
• \SimplePie\SimplePie::__construct()
• WP_SimplePie_Sanitize_KSES::__construct()
• SimplePie_Cache::register()
• WP_Error::__construct()Initializes the error.
• \SimplePie\SimplePie::merge_items()

Used by · 6

• WP_Widget_RSS::widget()Outputs the content for the current RSS widget instance.
• render_block_core_rss()Renders the `core/rss` block on server.
• wp_dashboard_plugins_output()Display plugins text for the WordPress news widget.
• wp_dashboard_rss_control()Sets up the RSS dashboard widget control and $args to be used as input to wp_widget_rss_form().
• wp_widget_rss_output()Displays the RSS entries in a list.
• wp_widget_rss_process()Processes RSS feed widget data and optionally retrieve feed items.

Source code

View on Trac ↗View on GitHub ↗

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				);

Changelog

Introduced in 2.8.0. Unchanged from 6.7.7 through 7.1.0.

1. 6.7.7
2. 6.8.8
3. 6.9.7
4. 7.0.4
5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

Parsed data

Generated from the wordpress-develop 7.1.0 tag, from src/wp-includes/feed.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.

Corrections

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