public function retrieveValue($key, $global = false)
    {
        $ret = null;

        if ($this->_enabled) {
            $namespace = $this->_getQueueNamespace($global);
            $session = AnService::get('com:sessions', array('namespace' => $namespace->namespace));
            $queue = $session->get($namespace->queue, new stdClass());
            $ret = isset($queue[$key]) ? $queue[$key] : null;
        }

        return $ret;
    }