code: public function setParam($key, $value)
      {
          $this->params[$key] = $value;
          
          foreach ($this->forms as $form) {
              if (isset($form['__instance__'])
                  && is_object($form['__instance__'])
                  && method_exists($form['__instance__'], 'setParam')
              ) {
                  $form['__instance__']->setParam($key, $value);
              }
          }
          return $this;
      }
docs: Sets a formular parameter.
  
  @param string $key
  @param mixed $value
  @return \Core\Form\Container