急求phpmysql中where的有关问题

急求php mysql中where的问题
请各位大侠帮我看看
$select = $this->db->select();
$select->from(PREFIX . $this->_table.' as s', '*');
$select->where($this->db->quoteInto('s.parent_category_id=?',$param->goods_category_id));
if($param->display_order){
$select->where($this->db->quoteInfo('s.type_id in(1,2,3,4)')); 这一行不知道哪里错了
$select->where($this->db->quoteInfo('s.display_order=?',$param->display_order));
}
新手求助，谢谢

------解决方案--------------------
$select->where($this->db->quoteInfo('s.type_id in(?)'), array(1,2,3,4));试一试