遞歸實現

function   ad(){     $res=DB::table("category")->get();   $res= json_encode($res);    $res= json_decode($res,1);    $arr= $this->gettree($res,0);      var_dump($arr);} function  gettree($data,$pid){     $tree=[];     foreach ($data as $k=>$v){         if ($v['pid']==$pid){             $v['son']=$this->gettree($data,$v['id']);             $tree[]=$v;         }     }     return $tree; }