private function extractHeadersFromResponse() {
    $response = "";
    $code = $this->response->getStatusCode();
    $text = HttpUtil::getResponseTextForCode($code);
    $response .= sprintf(self::STATUS_LINE_FORMAT, $code, $text);

    foreach($this->response->getHeaderList() as $header) {
      $response .= sprintf("%s: %s%s",
                           $header->getKey(),
                           $header->getValue(),
                           self::CRLF);
    }
    $response .= self::CRLF;
    return $response;
  }