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filter is not described

pre_unschedule_hook filter-hook . WP 5.1.0

Filter to preflight or hijack clearing all events attached to the hook.

Returning a non-null value will short-circuit the normal unscheduling process, causing the function to return the filtered value instead.

For plugins replacing wp-cron, return the number of events successfully unscheduled (zero if no events were registered with the hook) or false if unscheduling one or more events fails.

Usage

add_filter( 'pre_unschedule_hook', 'filter_function_name_8402', 10, 2 );
function filter_function_name_8402( $pre, $hook ){
	// filter...

	return $pre;
}
$pre(null/array)
Value to return instead.
Default: null to continue unscheduling the hook
$hook(string)
Action hook, the execution of which will be unscheduled.

Where the hook is called

wp_unschedule_hook()
pre_unschedule_hook
wp-includes/cron.php 446
$pre = apply_filters( 'pre_unschedule_hook', null, $hook );

Where the hook is used (in WP core)

Does not used.