thinkPHP和ajax实现的省市县区三级联动地址的请求方法

//选择地址
    public function getAddress(){
        $this->model = M('China');
        $type = I('post.type');
        switch ($type){
            case 1: //选择一级省份
                $this->getFirst();
                break;
            case 2: //选择二级市
                $pid = I('post.pid');
                $this->getSecond($pid);
                break;
            case 3: //选择三级县区
                $cid = I('post.pid');
                $this->getThird($cid);
                break;
            default:
                break;
        }
    }