方法：

static public function getChildren($data,$pid){        $arr=array();        foreach ($data as $v) {            if ($v['pid']==$pid) {                $arr[]=$v;                $arr=array_merge($arr,self::getChildren($data,$v['id']));            }        }        return $arr;    }

调用：

     array(                        'id'=>1,                        'pid'=>0                    ),                '1'=>array(                        'id'=>2,                        'pid'=>0                    ),                '2'=>array(                        'id'=>3,                        'pid'=>1                    ),                '3'=>array(                        'id'=>4,                        'pid'=>3                    )            );        //$data=Cate::unlimitedForLevel($data);        //$data=Cate::unlimitedForLayer($data);        //$data=Cate::getParents($data,4);        $data=Cate::getChildren($data,1);        echo '
';        print_r($data);die;        echo '
';        $this->display();            }}

效果：