如何检查第一条规则是否有效,然后不需要检查第二条/第三条规则,例如:
$this->form_validation->set_rules('children','Do you have children?','required');// e.g : answer no!
$this->form_validation->set_rules('son','How many sons?','required');//second rule
$this->form_validation->set_rules('daughter','How many daughter?','required');//third rule