public function addCallback($name, $callback, $prio = 10)
    {
        if (!is_callable($callback)) {
            throw new \Exception("Callback not callable.", 3);
            return false;
        }
        $key = $this->getCallbackKey($callback);
        if (!isset(self::$_baseRealCallbacks[$key])) {
            self::$_baseRealCallbacks[$key] = $callback;
        }

        $this->_callbacks[$name][$prio][] = $key;
        ksort($this->_callbacks[$name]);

        return $this;
    }