WP_Hook::add_filter( string $tag, callable $function_to_add, int $priority, int $accepted_args )

Hooks a function or method to a specific filter action.


Parameters

$tag

(Required) The name of the filter to hook the $function_to_add callback to.

$function_to_add

(Required) The callback to be run when the filter is applied.

$priority

(Required) The order in which the functions associated with a particular action 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 action.

$accepted_args

(Required) The number of arguments the function accepts.


Source

File: wp-includes/class-wp-hook.php

	public function add_filter( $tag, $function_to_add, $priority, $accepted_args ) {
		$idx = _wp_filter_build_unique_id( $tag, $function_to_add, $priority );
		$priority_existed = isset( $this->callbacks[ $priority ] );

		$this->callbacks[ $priority ][ $idx ] = array(
			'function' => $function_to_add,
			'accepted_args' => $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 );
		}

		if ( $this->nesting_level > 0 ) {
			$this->resort_active_iterations( $priority, $priority_existed );
		}
	}


Changelog

Changelog
Version Description
WP-4.7.0 Introduced.