private function getSerializationFormat(ReflectionClass $reflectionClass)
    {
        if ($this->isPhpVersionWithBrokenSerializationFormat()
            && $reflectionClass->implementsInterface('Serializable')
        ) {
            return self::SERIALIZATION_FORMAT_USE_UNSERIALIZER;
        }

        return self::SERIALIZATION_FORMAT_AVOID_UNSERIALIZER;
    }