code: protected function getRequestString()
      {
          $params = array_merge($this->getParams, $this->postParams, $this->getOauthParameters());
  
          $params = $this->curl->getParams($params);
  
          return rawurlencode($params);
      }
docs: Converting all parameters agetrrays to a single string with encoded values
  
  @return string  Single string with encoded values