巧妙使用php引用实现无限分类，输出层级数组

function getDataTree($rows, $id='id',$pid = 'parentid',$child = 'child',$root=0) {      $tree = array(); // 树 
        if(is_array($rows)){
             $array = array();
             foreach ($rows as $key=>$item){
             $array[$item[$id]] =& $rows[$key];
         }
         foreach($rows as $key=>$item){
             $parentId = $item[$pid];
             if($root == $parentId){
                 $tree[] =&$rows[$key];
             }else{
                 if(isset($array[$parentId])){
                     $parent =&$array[$parentId];
                     $parent[$child][]=&$rows[$key];
                 }
             }
         }
     }
     return $tree;
}