WP_Site_Health::check_for_page_caching(): WP_Error|array

Compatibility

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

Return value

WP_Error|array

Page cache detection details or else error information.

• $advanced_cache_presentbool

  Whether a page cache plugin is present.

• $page_caching_response_headersarray[]

  Sets of client caching headers for the responses.

• $response_timingfloat[]

  Response timings.

Performance profile

How much work a call to WP_Site_Health::check_for_page_caching() 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

Expensive

Reaches an outbound HTTP request via wp_remote_get().

Scaling

Scales with input

The body loops, so the work grows with how much data it finds.

Instructions

32–86

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 143.

Plugin surface

2 hooks

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

Called by

1

1 place 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
• httpoutbound HTTP requestwp_remote_get()called directly
• filesystemfilesystem accessfile_exists()called directly

Further down the call graph this can also reach option, 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 · 8 distinct outcomes

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

Hooks and filters fired · 2

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

1. 1
   apply_filters( https_local_ssl_verify )filterline 3615 (+3 into the body)

   Filters whether SSL should be verified for local HTTP API requests.

2. 2
   apply_filters( enable_loading_advanced_cache_dropin )filterline 3671 (+59 into the body)

   Filters whether to enable loading of the advanced-cache.php drop-in.

Uses · 10

• apply_filters()Calls the callback functions that have been added to a filter hook.
• home_url()Retrieves the URL for the current site where the front end is accessible.
• wp_unslash()Removes slashes from a string or recursively removes slashes from strings within an array.
• wp_remote_get()Performs an HTTP request using the GET method and returns its response.
• is_wp_error()Checks whether the given variable is a WordPress Error.
• wp_remote_retrieve_response_code()Retrieves only the response code from the raw response.
• wp_remote_retrieve_response_message()Retrieves only the response message from the raw response.
• wp_remote_retrieve_header()Retrieves a single header by name from the raw response.
• WP_Site_Health::get_page_cache_headers()Returns a mapping from response headers to an optional callback to verify if page cache is enabled or not.
• WP_Error::__construct()Initializes the error.

Used by · 1

• WP_Site_Health::get_page_cache_detail()Gets page cache details.

Source code

View on Trac ↗View on GitHub ↗

3612	private function check_for_page_caching() {3613 3614		/** This filter is documented in wp-includes/class-wp-http-streams.php */3615		$sslverify = apply_filters( 'https_local_ssl_verify', false, home_url( '/' ) );3616 3617		$headers = array();3618 3619		/*3620		 * Include basic auth in loopback requests. Note that this will only pass along basic auth when user is3621		 * initiating the test. If a site requires basic auth, the test will fail when it runs in WP Cron as part of3622		 * wp_site_health_scheduled_check. This logic is copied from WP_Site_Health::can_perform_loopback().3623		 */3624		if ( isset( $_SERVER['PHP_AUTH_USER'] ) && isset( $_SERVER['PHP_AUTH_PW'] ) ) {3625			$headers['Authorization'] = 'Basic ' . base64_encode( wp_unslash( $_SERVER['PHP_AUTH_USER'] ) . ':' . wp_unslash( $_SERVER['PHP_AUTH_PW'] ) );3626		}3627 3628		$caching_headers               = $this->get_page_cache_headers();3629		$page_caching_response_headers = array();3630		$response_timing               = array();3631 3632		for ( $i = 1; $i <= 3; $i++ ) {3633			$start_time    = microtime( true );3634			$http_response = wp_remote_get( home_url( '/' ), compact( 'sslverify', 'headers' ) );3635			$end_time      = microtime( true );3636 3637			if ( is_wp_error( $http_response ) ) {3638				return $http_response;3639			}3640			if ( wp_remote_retrieve_response_code( $http_response ) !== 200 ) {3641				return new WP_Error(3642					'http_' . wp_remote_retrieve_response_code( $http_response ),3643					wp_remote_retrieve_response_message( $http_response )3644				);3645			}3646 3647			$response_headers = array();3648 3649			foreach ( $caching_headers as $header => $callback ) {3650				$header_values = wp_remote_retrieve_header( $http_response, $header );3651				if ( empty( $header_values ) ) {3652					continue;3653				}3654				$header_values = (array) $header_values;3655				if ( empty( $callback ) || ( is_callable( $callback ) && count( array_filter( $header_values, $callback ) ) > 0 ) ) {3656					$response_headers[ $header ] = $header_values;3657				}3658			}3659 3660			$page_caching_response_headers[] = $response_headers;3661			$response_timing[]               = ( $end_time - $start_time ) * 1000;3662		}3663 3664		return array(3665			'advanced_cache_present'        => (3666				file_exists( WP_CONTENT_DIR . '/advanced-cache.php' )3667				&&3668				( defined( 'WP_CACHE' ) && WP_CACHE )3669				&&3670				/** This filter is documented in wp-settings.php */3671				apply_filters( 'enable_loading_advanced_cache_dropin', true )3672			),3673			'page_caching_response_headers' => $page_caching_response_headers,3674			'response_timing'               => $response_timing,3675		);3676	}

Changelog

Introduced in 6.1.0. 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-admin/includes/class-wp-site-health.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.

Corrections

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