WP_Site_Health::get_page_cache_headers(): array<string,

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

array<string,

?callable> Mapping of page caching headers and their (optional) verification callbacks.
A null value means a simple existence check is used for the header.

Performance profile

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

Trivial

Touches nothing outside its own arguments.

Scaling

Constant

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

Instructions

4

Executed per call on PHP 8.5. The body compiles to 74.

Plugin surface

1 hook

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

Called by

2

2 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

What one call costs · 1 distinct outcome

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

Hooks and filters fired · 1

One hook fires while WP_Site_Health::get_page_cache_headers() runs, in this order:

1. 1
   apply_filters( site_status_page_cache_supported_cache_headers )filterline 3596 (+117 into the body)

   Filters the list of cache headers supported by core.

Uses · 1

• apply_filters()Calls the callback functions that have been added to a filter hook.

Used by · 2

• WP_Site_Health::check_for_page_caching()Checks if site has page cache enabled or not.
• WP_Site_Health::get_test_page_cache()Tests if a full page cache is available.

Source code

View on Trac ↗View on GitHub ↗

3479	public function get_page_cache_headers(): array {3480 3481		$cache_hit_callback = static function ( $header_value ) {3482			return 1 === preg_match( '/(^| |,)HIT(,| |$)/i', $header_value );3483		};3484 3485		$cache_headers = array(3486			// Standard HTTP caching headers.3487			'cache-control'          => static function ( $header_value ) {3488				return (bool) preg_match( '/max-age=[1-9]/', $header_value );3489			},3490			'expires'                => static function ( $header_value ) {3491				return strtotime( $header_value ) > time();3492			},3493			'age'                    => static function ( $header_value ) {3494				return is_numeric( $header_value ) && $header_value > 0;3495			},3496			'last-modified'          => null,3497			'etag'                   => null,3498			'via'                    => null,3499 3500			/**3501			 * Custom caching headers.3502			 *3503			 * These do not seem to be actually used by any caching layers. There were first introduced in a Site Health3504			 * test in the AMP plugin. They were copied into the Performance Lab plugin's Site Health test before they3505			 * were merged into core.3506			 *3507			 * @link https://github.com/ampproject/amp-wp/pull/68493508			 * @link https://github.com/WordPress/performance/pull/2633509			 * @link https://core.trac.wordpress.org/changeset/540433510			 */3511			'x-cache-enabled'        => static function ( $header_value ) {3512				return ( 'true' === strtolower( $header_value ) );3513			},3514			'x-cache-disabled'       => static function ( $header_value ) {3515				return ( 'on' !== strtolower( $header_value ) );3516			},3517 3518			/**3519			 * CloudFlare.3520			 *3521			 * @link https://developers.cloudflare.com/cache/concepts/cache-responses/3522			 */3523			'cf-cache-status'        => $cache_hit_callback,3524 3525			/**3526			 * Fastly.3527			 *3528			 * @link https://www.fastly.com/documentation/reference/http/http-headers/X-Cache/3529			 */3530			'x-cache'                => $cache_hit_callback,3531 3532			/**3533			 * LightSpeed.3534			 *3535			 * @link https://docs.litespeedtech.com/lscache/devguide/controls/#x-litespeed-cache3536			 */3537			'x-litespeed-cache'      => $cache_hit_callback,3538 3539			/**3540			 * OpenResty srcache-nginx-module.3541			 *3542			 * The `x-srcache-store-status` header indicates if the response was stored in the cache.3543			 * Valid values include `STORE` and `BYPASS`.3544			 *3545			 * The `x-srcache-fetch-status` header indicates if the response was fetched from the cache.3546			 * Valid values include `HIT`, `MISS`, and `BYPASS`.3547			 *3548			 * @link https://github.com/openresty/srcache-nginx-module3549			 */3550			'x-srcache-store-status' => static function ( $header_value ) {3551				return 'store' === strtolower( $header_value );3552			},3553			'x-srcache-fetch-status' => $cache_hit_callback,3554 3555			/**3556			 * Nginx.3557			 *3558			 * @link https://blog.nginx.org/blog/nginx-caching-guide

Changelog

Introduced in 6.1.0. One change between 6.7.7 and 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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