private function getValue($property_key, $config = null, &$found)
    {
        if (null === $config) {
            $config = $this->config;
        }

        foreach ($config as $key => $value) {
            if ($key === $property_key) {
                $found = true;

                return $value;
            }
            if (is_array($value)) {
                $ret = $this->getValue($property_key, $value, $found);

                if (null !== $ret) {
                    return $ret;
                }
            }
        }
    }