nocache_headers()
- Since
- 2.0.0
- Source
wp-includes/functions.php:1538
Description
Different browsers support different nocache headers, so several headers must be sent so that all of them get the point that no caching should occur.
Compatibility
- WordPress
- since 2.0.0
- 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.
Performance profile
How much work a call to 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
- Light
- Scaling
- Scales with input
- Instructions
- 4–14
- Plugin surface
- None
- Called by
- 11
Touches nothing outside its own arguments.
The body loops, so the work grows with how much data it finds.
Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 23.
Nothing here hands control to plugin code.
11 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()one call below nocache_headers()
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 nocache_headers() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
headers_sent() | 4 | headers_sent() |
!headers_sent() | 13–14 | headers_sent(), wp_get_nocache_headers(), header_remove() |
Across PHP versions
Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 23 instructions, 4–14 executed per call, 3 branches. 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.
Uses · 1
- wp_get_nocache_headers()Gets the HTTP header information to prevent caching.
Used by · 11
- WP::handle_404()Set the Headers for 404, if nothing is found for requested URL.
- WP_Customize_Manager::customize_preview_init()Prints JavaScript settings.
- _ajax_wp_die_handler()Kills WordPress execution and displays Ajax response with an error message.
- _default_wp_die_handler()Kills WordPress execution and displays HTML page with an error message.
- _json_wp_die_handler()Kills WordPress execution and displays JSON response with an error message.
- _jsonp_wp_die_handler()Kills WordPress execution and displays JSONP response with an error message.
- _xml_wp_die_handler()Kills WordPress execution and displays XML response with an error message.
- _xmlrpc_wp_die_handler()Kills WordPress execution and displays XML response with an error message.
- auth_redirect()Checks if a user is logged in, if not it redirects them to the login page.
- wp_not_installed()Redirects to the installer if WordPress is not installed.
- wp_start_scraping_edited_file_errors()Starts scraping edited file errors.
Source code
function nocache_headers() { if ( headers_sent() ) { return; } $headers = wp_get_nocache_headers(); unset( $headers['Last-Modified'] ); header_remove( 'Last-Modified' ); foreach ( $headers as $name => $field_value ) { header( "{$name}: {$field_value}" ); }}Changelog
Introduced in 2.0.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
About this page
- Parsed data
- Generated from the wordpress-develop 6.9.7 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.