code: public function getHtml($error = null, $use_ssl = false) {
          if ( ! $this->getPublicKey()) {
              throw new \Exception('To use reCAPTCHA you must get an API key from <a href="https://www.google.com/recaptcha/admin/create">https://www.google.com/recaptcha/admin/create</a>');
          }
  
          if (true === $use_ssl) {
              $server = self::RECAPTCHA_API_SECURE_SERVER;
          } else {
              $server = self::RECAPTCHA_API_SERVER;
          }
  
          $errorpart = '';
          if ($error) {
              $errorpart = "&amp;error=" . $error;
          }
  
          return '<script type="text/javascript" src="'. $server . '/challenge?k=' . $this->getPublicKey() . $errorpart . '"></script>'. PHP_EOL
                  .'<noscript>'. PHP_EOL
                  .'    <iframe src="'. $server . '/noscript?k=' . $this->getPublicKey() . $errorpart . '" height="300" width="500" frameborder="0"></iframe><br/>'. PHP_EOL
                  .'    <textarea name="recaptcha_challenge_field" rows="3" cols="40"></textarea>'. PHP_EOL
                  .'    <input type="hidden" name="recaptcha_response_field" value="manual_challenge"/>'. PHP_EOL
                  .'</noscript>'. PHP_EOL;
      }
docs: Gets the challenge HTML (javascript and non-javascript version).
  This is called from the browser, and the resulting reCAPTCHA HTML widget
  is embedded within the HTML form it was called from.
  
  @param string $error The error given by reCAPTCHA (optional, default is null)
  @param boolean $use_ssl Should the request be made over ssl? (optional, default is false)
  @return string The HTML to be embedded in the user's form.
  @throws \Exception