Payu\Serializer\SerializerAbstract::calculateHash PHP Method

    protected function calculateHash($rawData)
    {
        ksort($rawData);
        $buffer = '';
        foreach ($rawData as $key => $value) {
            $buffer .= strlen($value) . $value;
        }
        return hash_hmac('md5', $buffer, $this->configuration->getSecretKey());
    }