code: public function submitFormById($id, $additional = false)
      {
          if (! ($form = $this->page->getFormById($id))) {
              return false;
          }
          $success = $this->load(
                  $form->getAction(),
                  $form->submit($additional));
  
          return ($success ? $this->getContent() : $success);
      }
docs: Submits a form by the ID.
  
  @param string $id       The form ID. No submit button value will be sent.
  
  @return string/boolean  Page on success.