1 // demo data
 2 var data = {
 3   name: 'My Tree',
 4   children: [
 5     { name: 'hello' },
 6     { name: 'wat' },
 7     {
 8       name: 'child folder',
 9       children: [
10         {
11           name: 'child folder',
12           children: [
13             { name: 'hello' },
14             { name: 'wat' }
15           ]
16         },
17         { name: 'hello' },
18         { name: 'wat' },
19         {
20           name: 'child folder',
21           children: [
22             { name: 'hello' },
23             { name: 'wat' }
24           ]
25         }
26       ]
27     }
28   ]
29 }

 1     public function show($user_id)
 2     {
 3         $arr = array();
 4 
 5         $data = DB::table("directory")->where('user_id', $user_id)->get();
 6         if ($data->isEmpty()) {
 7             return "no data!";
 8         }
 9         //组合数据
10         foreach ($data as $k => $v) {
11             array_push($arr, array('id' => $v->id, 'name' => $v->name, 'pid' => $v->parent_id));
12         }
13         //结果：
14         //  $arr = array(
15         //      array('id'=>1,'name'='视频','pid'=>0),
16         //      array('id'=>2,'name'='图片','pid'=>0),
17         //      array('id'=>3,'name'='科幻','pid'=>1),
18         //      array('id'=>4,'name'='音乐','pid'=>0),
19         //      array('id'=>5,'name'='流行','pid'=>4),
20         //      array('id'=>6,'name'='变形金刚','pid'=>3),
21         //      array('id'=>7,'name'='风景','pid'=>2),  
22         //  )
23         function get_attr($a, $pid)
24         {
25             $tree = array(); //每次都声明一个新数组用来放子元素
26             foreach ($a as $v) {
27                 if ($v['pid'] == $pid) {
28                     //匹配子记录
29                     $v['children'] = get_attr($a, $v['id']); //递归获取子记录
30                     if ($v['children'] == null) {
31                         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）
32                     }
33                     $tree[] = $v; //将记录存入新数组
34                 }
35             }
36             return $tree; //返回新数组
37         }
38         return get_attr($arr, 0);
39     }

[
  {
    "id": 1,
    "name": "视频",
    "pid": 0,
    "children": [
      {
        "id": 4,
        "name": "科幻",
        "pid": 1,
        "children": [
          {
            "id": 6,
            "name": "变形金刚",
            "pid": 4
          }
        ]
      }
    ]
  },
  {
    "id": 2,
    "name": "图片",
    "pid": 0,
    "children": [
      {
        "id": 7,
        "name": "风景",
        "pid": 2
      }
    ]
  },
  {
    "id": 3,
    "name": "音乐",
    "pid": 0,
    "children": [
      {
        "id": 5,
        "name": "流行",
        "pid": 3
      }
    ]
  }
]