PHP无限级分类实现（递归+非递归）

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 /**
  * Created by PhpStorm.
  * User: qishou
  * Date: 15-8-2
  * Time: 上午12:00
  */
 //准备数组，代替从数据库中检索出的数据(共有三个必须字段id,name,pid)
 header("content-type:text/html;charset=utf-8");
 $categories = array(
     array('id'=>1,'name'=>'电脑','pid'=>0),
     array('id'=>2,'name'=>'手机','pid'=>0),
     array('id'=>3,'name'=>'笔记本','pid'=>1),
     array('id'=>4,'name'=>'台式机','pid'=>1),
     array('id'=>5,'name'=>'智能机','pid'=>2),
     array('id'=>6,'name'=>'功能机','pid'=>2),
     array('id'=>7,'name'=>'超级本','pid'=>3),
     array('id'=>8,'name'=>'游戏本','pid'=>3),
 );

 /*======================非递归实现========================*/
 $tree = array();
 //第一步，将分类id作为数组key,并创建children单元
 foreach($categories as $category){
     $tree[$category['id']] = $category;
     $tree[$category['id']]['children'] = array();
 }
 //第二步，利用引用，将每个分类添加到父类children数组中，这样一次遍历即可形成树形结构。
 foreach($tree as $key=>$item){
     if($item['pid'] != 0){
         $tree[$item['pid']]['children'][] = &$tree[$key];//注意：此处必须传引用否则结果不对
         if($tree[$key]['children'] == null){
             unset($tree[$key]['children']); //如果children为空，则删除该children元素（可选）
         }
     }
 }
 ////第三步，删除无用的非根节点数据
 foreach($tree as $key=>$category){
     if($category['pid'] != 0){
         unset($tree[$key]);
     }
 }

 print_r($tree);

 /*======================递归实现========================*/
 $tree = $categories;
 function get_attr($a,$pid){
     $tree = array();                                //每次都声明一个新数组用来放子元素
     foreach($a as $v){
         if($v['pid'] == $pid){                      //匹配子记录
             $v['children'] = get_attr($a,$v['id']); //递归获取子记录
             if($v['children'] == null){
                 unset($v['children']);             //如果子元素为空则unset()进行删除，说明已经到该分支的最后一个元素了（可选）
             }
             $tree[] = $v;                           //将记录存入新数组
         }
     }
     return $tree;                                  //返回新数组
 }
 echo "";

 print_r(get_attr($tree,0));

转自：http://blog.csdn.net/qishouzhang/article/details/47204359