private function calculateSignatureAndParametersToString($parameters = array())
 {
     $parameters['AWSAccessKeyId'] = $this->config->getAccessKey();
     $parameters['Version'] = self::SERVICE_VERSION;
     $parameters['SignatureMethod'] = 'HmacSHA256';
     $parameters['SignatureVersion'] = 2;
     $parameters['Timestamp'] = $this->getFormattedTimestamp();
     uksort($parameters, 'strcmp');
     $this->createServiceUrl();
     $parameters['Signature'] = $this->signParameters($parameters);
     $parameters = $this->getParametersAsString($parameters);
     // Save these parameters in the parameters variable so that it can be returned for unit testing.
     $this->parameters = $parameters;
     return $parameters;
 }