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@stevegrunwell
Created February 14, 2017 20:06
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Enables action and filter callbacks to be executed exactly once via the WordPress Plugin API. https://engineering.growella.com/one-time-callbacks-wordpress-plugin-api/
<?php
/**
* Registers the "One time hook" functionality.
*
* Note that this file is intentionally in the *global* namespace!
*
* @author Growella
* @license MIT
*/
if ( ! function_exists( 'add_action_once' ) ) {
/**
* Register an action to run exactly one time.
*
* The arguments match that of add_action(), but this function will also register a second
* callback designed to remove the first immediately after it runs.
*
* @param string $hook The action name.
* @param callable $callback The callback function.
* @param int $priority Optional. The priority at which the callback should be executed.
* Default is 10.
* @param int $args Optional. The number of arguments expected by the callback function.
* Default is 1.
* @return bool Like add_action(), this function always returns true.
*/
function add_action_once( $hook, $callback, $priority = 10, $args = 1 ) {
$singular = function () use ( $hook, $callback, $priority, $args, &$singular ) {
call_user_func_array( $callback, func_get_args() );
remove_action( $hook, $singular, $priority, $args );
};
return add_action( $hook, $singular, $priority, $args );
}
}
if ( ! function_exists( 'add_filter_once' ) ) {
/**
* Register a filter to run exactly one time.
*
* The arguments match that of add_filter(), but this function will also register a second
* callback designed to remove the first immediately after it runs.
*
* @param string $hook The filter name.
* @param callable $callback The callback function.
* @param int $priority Optional. The priority at which the callback should be executed.
* Default is 10.
* @param int $args Optional. The number of arguments expected by the callback function.
* Default is 1.
* @return bool Like add_filter(), this function always returns true.
*/
function add_filter_once( $hook, $callback, $priority = 10, $args = 1 ) {
$singular = function () use ( $hook, $callback, $priority, $args, &$singular ) {
call_user_func_array( $callback, func_get_args() );
remove_filter( $hook, $singular, $priority, $args );
};
return add_filter( $hook, $singular, $priority, $args );
}
}
@kimhf
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kimhf commented May 8, 2018

Very nice solution. There is one issue when one or more add_action_once is called inside the callback. Ends with a crash in my case. Moving remove_action and remove_filter above call_user_func_array seems to solve it.

@thefrosty
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The remove_* functions only use 3 parameters, so passing the args array isn't needed.

@pfaciana
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pfaciana commented Apr 5, 2021

If it's a filter rather than action you need to return the value of call_user_func_array( $callback, func_get_args() ); on line 53. And since actions don't care about return values, you can it for both. You just need to swap lines 53 and 54, and then return line 54 like so...

remove_filter( $hook, $singular, $priority, $args );
return call_user_func_array( $callback, func_get_args() );

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