public function addFlash($key, $value = true, $removeAfterAccess = true)
    {
        $counters = $this->get($this->flashParam, []);
        $counters[$key] = $removeAfterAccess ? -1 : 0;
        $this->data[$this->flashParam] = $counters;
        if (empty($this->data[$key])) {
            $this->data[$key] = [$value];
        } else {
            if (is_array($this->data[$key])) {
                $this->data[$key][] = $value;
            } else {
                $this->data[$key] = [$this->data[$key], $value];
            }
        }
    }