WP_Hook::add_filter( string $hook_name, callable $callback, int $priority, int $accepted_args )
- Since
- 4.7.0
- Source
wp-includes/class-wp-hook.php:82
Compatibility
- WordPress
- since 4.7.0
- 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.
Parameters
$hook_namestring- The name of the filter to add the callback to.
$callbackcallable- The callback to be run when the filter is applied.
$priorityint- The order in which the functions associated with a particular filter are executed. Lower numbers correspond with earlier execution, and functions with the same priority are executed in the order in which they were added to the filter.
$accepted_argsint- The number of arguments the function accepts.
Performance profile
How much work a call to WP_Hook::add_filter() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.
- Cost class
- Trivial
- Scaling
- Constant
- Instructions
- 32–46
- Plugin surface
- None
- Called by
- 0
Touches nothing outside its own arguments.
No loop in the body: the same number of instructions runs whatever you pass in.
Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 46.
Nothing here hands control to plugin code.
Nothing in core calls this; the cost is only what you spend yourself.
What one call costs · 4 distinct outcomes
One number would be a lie: the work depends on which branch runs. These are every distinct cost WP_Hook::add_filter() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
| always | 32–37 | _wp_filter_build_unique_id(), array_keys() |
| always | 36–41 | _wp_filter_build_unique_id(), array_keys(), ->resort_active_iterations() |
!isset($priority) | 41–42 | _wp_filter_build_unique_id(), ksort(), array_keys() |
!isset($priority) | 45–46 | _wp_filter_build_unique_id(), ksort(), array_keys(), ->resort_active_iterations() |
Across PHP versions
Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 46 instructions, 32–46 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 · 2
- _wp_filter_build_unique_id()Builds a unique string ID for a hook callback function.
- WP_Hook::resort_active_iterations()Handles resetting callback priority keys mid-iteration.
Source code
public function add_filter( $hook_name, $callback, $priority, $accepted_args ) { if ( null === $priority ) { $priority = 0; } $idx = _wp_filter_build_unique_id( $hook_name, $callback, $priority ); $priority_existed = isset( $this->callbacks[ $priority ] ); $this->callbacks[ $priority ][ $idx ] = array( 'function' => $callback, 'accepted_args' => (int) $accepted_args, ); // If we're adding a new priority to the list, put them back in sorted order. if ( ! $priority_existed && count( $this->callbacks ) > 1 ) { ksort( $this->callbacks, SORT_NUMERIC ); } $this->priorities = array_keys( $this->callbacks ); if ( $this->nesting_level > 0 ) { $this->resort_active_iterations( $priority, $priority_existed ); } }Changelog
Introduced in 4.7.0. 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/class-wp-hook.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it. - Corrections
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