php 数组处理成无限极分类的方法

 public  function getSubTree($data , $id = 0 , $lev = 0) {

        $son = array();
        $stack = array();
        $stack_tmp = array(); //存下层节点的id们
        $tree= array();

        $stack[] = $id;

        while(!empty($data)){

            foreach ($stack as $k1 => $v1){

                foreach ($data as $key =>$value){
                    if($value['pid'] == $v1){
                        $value['level'] = $lev;
                        $son[] = $value;
                        unset($data[$key]);
                        array_push($stack_tmp , $value['id']);
                        $tree[$lev][] = $value;
                    }
                }

            }

            $stack = array();
            $stack = $stack_tmp;
            $stack_tmp = array();

            $lev+=1;

        }

        $num = count($tree)-1;

        for($i=$num;$i>0;$i--){
            $j = $i -1;
            foreach ($tree[$j] as $k1=>&$v1){
                foreach ($tree[$i] as $k2=>&$v2){
                    if($v2['pid'] == $v1['id']){
                        $v1['child'][] = $v2;
                        unset($tree[$i][$k2]);
                    }
                }
            }
            unset($tree[$i]);
        }
        return $tree;
    }