WordPress at a glance
function is not described

WP_Hook::key() public WP 4.7.0

Returns the key of the current element.

It's a method of the class: WP_Hook{}

No Hooks.

Return

Mixed. Returns current priority on success, or NULL on failure

Usage

$WP_Hook = new WP_Hook();
$WP_Hook->key();

Changelog

Since 4.7.0 Introduced.

Code of WP_Hook::key() WP 5.5.1

<?php
public function key() {
	return key( $this->callbacks );
}