WordPress at a glance
function is not described

shutdown_action_hook() WP 1.2.0

Runs just before PHP shuts down execution.

Hooks in function
Return

Nothing (null).

Usage

shutdown_action_hook();

Code of shutdown action hook: wp-includes/load.php VER 5.0.3

<?php
function shutdown_action_hook() {
	/**
	 * Fires just before PHP shuts down execution.
	 *
	 * @since 1.2.0
	 */
	do_action( 'shutdown' );

	wp_cache_close();
}