Symfony\Component\Form\AbstractType::getDefaultOptions PHP Method

    public function getDefaultOptions(array $options)
    {
        return array();
    }

 public function getDefaultOptions(array $options)
 {
     $options = parent::getDefaultOptions($options);
     $options['url'] = false;
     $options['url_params'] = array();
     $options['callback'] = false;
     $options['select_callback'] = false;
     //DEFAULT VALUE = NULL
     $options['empty_value'] = "";
     return $options;
 }