protected function magicIsset($key)
    {
        if (!$this->magicInited) {
            $this->magicInit();
        }
        $exists = &$this->magicFields['exists'];
        if (!array_key_exists($key, $exists)) {
            if (array_key_exists($key, $this->magicFields['fields'])) {
                $exists[$key] = true;
            } elseif (isset($this->magicFields['loaders'][$key])) {
                $exists[$key] = true;
            } else {
                $exists[$key] = $this->magicExistsField($key);
            }
        }
        return $exists[$key];
    }