code: protected function createRequest($url, $encoding)
      {
          $request = $this->createHttpRequest($url, $encoding);
          $this->addAdditionalHeaders($request);
          if ($this->cookies_enabled) {
              $request->readCookiesFromJar($this->cookie_jar, $url);
          }
          $this->authenticator->addHeaders($request, $url);
  
          // Add referer header, if not set explicitly
          if($this->http_referer) {
              $headers = $request->getHeaders();
              if(is_array($headers)) {
                  $custom_referer = false;
                  foreach ($headers as $header) {
                      if (preg_match('~^referer:~i', $header)) {
                          $custom_referer = true;
                          break;
                      }
                  }
                  if (! $custom_referer) {
                      $request->addHeaderLine('Referer: ' . $this->http_referer);
                  }
              }
          }
  
          return $request;
      }
docs: Creates a full page request.
  
  @param SimpleUrl $url                 Target to fetch as url object.
  @param SimpleFormEncoding $encoding   POST/GET parameters.
  
  @return SimpleHttpRequest             New request.