code: public function disableForm($key = null)
      {
          if (null === $key) {
              $this->activeForms = array();
              return $this;
          }
          
          if (!is_array($key)) {
              $key = array($key);
          }
          
          foreach ($key as $k) {
              if (false !== strpos($k, '.')) {
                  list($childKey, $childForm) = explode('.', $k, 2);
                  $child = $this->getForm($childKey);
                  $child->disableForm($childForm);
              } elseif (isset($this->forms[$k]['__instance__'])) {
                  unset($this->forms[$k]['__instance__']);
              }
          }
          $this->activeForms = array_filter(
              $this->activeForms,
              function ($item) use ($key) {
                  return !in_array($item, $key);
              }
          );
          
          return $this;
      }
docs: Disables a formular.
  
  @param string $key
  
  @return self