wp_get_nocache_headers(): array
- Since
- 2.8.0, 6.3.0, 6.8.0
- Source
wp-includes/functions.php:1508
Description
The several different headers cover the different ways cache prevention is handled by different browsers or intermediate caches such as proxy servers.
Compatibility
- WordPress
- since 6.8.0
- PHP
- 7.4–8.6-dev
- 6.7.7
- 6.8.8
- 6.9.7
- 7.0.4
- 7.1.0
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- The associative array of header names and field values.
Performance profile
How much work a call to wp_get_nocache_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
- Scaling
- Constant
- Instructions
- 8–14
- Plugin surface
- 1 hook
- Called by
- 3
Touches nothing outside its own arguments.
No loop in the body: the same number of instructions runs whatever you pass in.
Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 14.
Third-party callbacks on 'nocache_headers' run inside this call, and their cost is not bounded by anything here.
3 places in core call this, so the cost is paid more often than your own code shows.
What it touches
- hookthird-party callbacks
apply_filters()called directly
What one call costs · 2 distinct outcomes
One number would be a lie: the work depends on which branch runs. These are every distinct cost wp_get_nocache_headers() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
!function_exists() | 8 | function_exists() |
function_exists() | 14 | function_exists(), apply_filters() |
Across PHP versions
Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 14 instructions, 8–14 executed per call, 1 branch. The work does not change between versions.
An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.
Hooks and filters fired · 1
One hook fires while wp_get_nocache_headers() runs, in this order:
- apply_filters( nocache_headers )filterline 1526 (+18 into the body)
Filters the cache-controlling HTTP headers that are used to prevent caching.
Uses · 1
- apply_filters()Calls the callback functions that have been added to a filter hook.
Used by · 3
- WP::send_headers()Sends additional HTTP headers for caching, content type, etc.
- WP_REST_Server::serve_request()Handles serving a REST API request.
- nocache_headers()Sets the HTTP headers to prevent caching for the different browsers.
Source code
function wp_get_nocache_headers() { $cache_control = 'no-cache, must-revalidate, max-age=0, no-store, private'; $headers = array( 'Expires' => 'Wed, 11 Jan 1984 05:00:00 GMT', 'Cache-Control' => $cache_control, ); if ( function_exists( 'apply_filters' ) ) { /** * Filters the cache-controlling HTTP headers that are used to prevent caching. * * @since 2.8.0 * * @see wp_get_nocache_headers() * * @param array $headers Header names and field values. */ $headers = (array) apply_filters( 'nocache_headers', $headers ); } $headers['Last-Modified'] = false; return $headers;}Changelog
Introduced in 2.8.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
Cache-Control header now includes the no-store and private directives regardless of whether a user is logged in.from the docblockCache-Control header for logged in users now includes the no-store and private directives.from the docblockAbout this page
- Parsed data
- Generated from the wordpress-develop 7.1.0 tag, from
src/wp-includes/functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it. - Corrections
- Something wrong on this page? Report it and it gets fixed in the next regeneration.