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

Compatibility

Present in every tracked release (6.7.10 to 7.1.3), 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

Moderate

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

Scaling

Constant

No loop in the body: the same number of instructions runs whatever you pass in.

Instructions

75–86

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 95.

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 · 4 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 832 (+32 into the body)

   Filters the transient lifetime of the feed cache.

2. 2
   do_action( wp_feed_options )actionline 842 (+42 into the body)

   Fires just before processing the SimplePie feed object.

Uses · 7

• 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.
• \SimplePie\SimplePie::__construct()
• WP_SimplePie_Sanitize_KSES::__construct()
• SimplePie_Cache::register()
• WP_Error::__construct()Initializes the error.

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()Display the RSS entries in a list.
• wp_widget_rss_process()Process RSS feed widget data and optionally retrieve feed items.

Source code

View on Trac ↗View on GitHub ↗

800function fetch_feed( $url ) {801	if ( ! class_exists( 'SimplePie\SimplePie', false ) ) {802		require_once ABSPATH . WPINC . '/class-simplepie.php';803	}804 805	require_once ABSPATH . WPINC . '/class-wp-feed-cache-transient.php';806	require_once ABSPATH . WPINC . '/class-wp-simplepie-file.php';807	require_once ABSPATH . WPINC . '/class-wp-simplepie-sanitize-kses.php';808 809	$feed = new SimplePie\SimplePie();810 811	$feed->set_sanitize_class( 'WP_SimplePie_Sanitize_KSES' );812	/*813	 * We must manually overwrite $feed->sanitize because SimplePie's constructor814	 * sets it before we have a chance to set the sanitization class.815	 */816	$feed->sanitize = new WP_SimplePie_Sanitize_KSES();817 818	// Register the cache handler using the recommended method for SimplePie 1.3 or later.819	if ( method_exists( 'SimplePie_Cache', 'register' ) ) {820		SimplePie_Cache::register( 'wp_transient', 'WP_Feed_Cache_Transient' );821		$feed->set_cache_location( 'wp_transient' );822	} else {823		// Back-compat for SimplePie 1.2.x.824		require_once ABSPATH . WPINC . '/class-wp-feed-cache.php';825		$feed->set_cache_class( 'WP_Feed_Cache' );826	}827 828	$feed->set_file_class( 'WP_SimplePie_File' );829 830	$feed->set_feed_url( $url );831	/** This filter is documented in wp-includes/class-wp-feed-cache-transient.php */832	$feed->set_cache_duration( apply_filters( 'wp_feed_cache_transient_lifetime', 12 * HOUR_IN_SECONDS, $url ) );833 834	/**835	 * Fires just before processing the SimplePie feed object.836	 *837	 * @since 3.0.0838	 *839	 * @param SimplePie\SimplePie $feed SimplePie feed object (passed by reference).840	 * @param string|string[]     $url  URL of feed or array of URLs of feeds to retrieve.841	 */842	do_action_ref_array( 'wp_feed_options', array( &$feed, $url ) );843 844	$feed->init();845	$feed->set_output_encoding( get_bloginfo( 'charset' ) );846 847	if ( $feed->error() ) {848		return new WP_Error( 'simplepie-error', $feed->error() );849	}850 851	return $feed;852}

Changelog

Introduced in 2.8.0. Unchanged from 6.7.10 through 7.1.3.

1. 6.7.10
2. 6.8.11
3. 6.9.10
4. 7.0.7
5. 7.1.3

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

About this page

Parsed data

Generated from the wordpress-develop 6.7.10 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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