public function register($hook, $callback, $priority = 0) {
		if (!isset($this->hooks[$hook])) {
			$this->hooks[$hook] = array();
		}
		if (!isset($this->hooks[$hook][$priority])) {
			$this->hooks[$hook][$priority] = array();
		}

		$this->hooks[$hook][$priority][] = $callback;
	}