wp_cron()
- Since
- 2.1.0, 5.1.0, 5.7.0, 6.9.0
- Source
wp-includes/cron.php:990
Description
The spawn_cron() function attempts to make a non-blocking loopback request to wp-cron.php (when alternative cron is not being used). However, the wp_remote_post() function does not always respect the timeout and blocking parameters. A timeout of 0.01 may end up taking 1 second. When this runs at the 'wp_loaded' action, it increases the Time To First Byte (TTFB) since the HTML cannot be sent while waiting for the cron request to initiate. Moving the spawning of cron to the 'shutdown' hook allows for the server to flush the HTML document to the browser while waiting for the request.
Compatibility
- WordPress
- since 6.9.0
- 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 wp_cron() 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
- 9–14
- Plugin surface
- None
- Called by
- 0
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 29.
Nothing here hands control to plugin code.
Nothing in core calls this; the cost is only what you spend yourself.
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 wp_cron() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
doing_action() | 9–11 | doing_action(), _wp_cron() |
!doing_action() | 11–13 | doing_action(), add_action() |
defined('ALTERNATE_WP_CRON') && did_action() | 11 | did_action(), _wp_cron() |
defined('ALTERNATE_WP_CRON') && !did_action() | 14 | did_action(), add_action() |
Across PHP versions
Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 29 instructions, 9–14 executed per call, 4 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 · 4
- did_action()Retrieves the number of times an action has been fired during the current request.
- _wp_cron()Runs scheduled callbacks or spawns cron for all scheduled events.
- add_action()Adds a callback function to an action hook.
- doing_action()Returns whether or not an action hook is currently being processed.
Source code
function wp_cron(): void { if ( defined( 'ALTERNATE_WP_CRON' ) && ALTERNATE_WP_CRON ) { if ( did_action( 'wp_loaded' ) ) { _wp_cron(); } else { add_action( 'wp_loaded', '_wp_cron', 20 ); } } elseif ( doing_action( 'shutdown' ) ) { _wp_cron(); } else { add_action( 'shutdown', '_wp_cron' ); }}Changelog
Introduced in 2.1.0. One change between 6.7.7 and 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
false|int|void to none.verified against sourceALTERNATE_WP_CRON is enabled; the function now always returns void.from the docblockAbout this page
- Parsed data
- Generated from the wordpress-develop 6.9.7 tag, from
src/wp-includes/cron.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.