public static function add_wp_hook( $tag, $function_to_add, $priority = 10, $accepted_args = 1 ) {
		global $wp_filter, $merged_filters;

		if ( function_exists( 'add_filter' ) ) {
			add_filter( $tag, $function_to_add, $priority, $accepted_args );
		} else {
			$idx = self::wp_hook_build_unique_id( $tag, $function_to_add, $priority );

			// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- This is intentional & the purpose of this function.
			$wp_filter[ $tag ][ $priority ][ $idx ] = array(
				'function'      => $function_to_add,
				'accepted_args' => $accepted_args,
			);
			unset( $merged_filters[ $tag ] );
		}

		return true;
	}