Php 将对象数组展平为指定值的数组

我使用Laravel 5.1获得了一组包含相关问题的类别

我只需要嵌套问题的id，但要使

选择

起作用，我需要指定联接列，即

类别id

：

    $categories = Category::with(['questions'=>function($query){
        $query->select('id', 'category_id');
    }])->get();

这让我明白：

[
 {
  "id": 1,
  "category": "Anatomy",
  "created_at": "2016-04-13 00:46:12",
  "updated_at": "2016-04-13 00:46:12",
  "questions":[
    {"id": 1, "category_id": 1},
    {"id": 2, "category_id": 1},
    {"id": 3, "category_id": 1},
    {"id": 4, "category_id": 1},
    ...
  ]
 }, ...
]

我如何才能让

问题：[

只包含ID而不是对象，所以应该是：

[
 {
  "id": 1,
  "category": "Anatomy",
  "created_at": "2016-04-13 00:46:12",
  "updated_at": "2016-04-13 00:46:12",
  "questions":[
     1, 2, 3, 4 ...
  ]
 }, ...
]

我已尝试使用map收集并列出ID。这不起作用：

    $test = collect($categories)->map(function ($q) {
        return collect($q)->lists('id')->toArray();
    });

---

我更喜欢在这里处理这个问题，所以我不需要在前端处理它。

这里有一个简单的方法

下面是一个根据您的数据复制的示例数据

[
 {
  "id": 1,
  "category": "Anatomy",
  "created_at": "2016-04-13 00:46:12",
  "updated_at": "2016-04-13 00:46:12",
  "questions":[
    {"id": 1, "category_id": 1},
    {"id": 2, "category_id": 1},
    {"id": 3, "category_id": 1},
    {"id": 4, "category_id": 1}
  ]
 }
]

下面是PHP代码

# JSON DATA
$data = '[
 {
  "id": 1,
  "category": "Anatomy",
  "created_at": "2016-04-13 00:46:12",
  "updated_at": "2016-04-13 00:46:12",
  "questions":[
    {"id": 1, "category_id": 1},
    {"id": 2, "category_id": 1},
    {"id": 3, "category_id": 1},
    {"id": 4, "category_id": 1}
  ]
 }
]';

# convert to array
# $data = json data
$categories = json_decode($data, true);

# assuming the categories has a list of object
# so i need to override it all
foreach ($categories as $key => $category) {

    # map a new array
    $list = array_map(function ($data) {
        return $data['id'];
    }, $category['questions']);
    # assign it to the current object being
    # iterated the new array created from
    # the array_map
    $categories[$key]['questions']  = $list;

}

输出将如下所示

[
  {
    "id": 1,
    "category": "Anatomy",
    "created_at": "2016-04-13 00:46:12",
    "updated_at": "2016-04-13 00:46:12",
    "questions": [
      1,
      2,
      3,
      4
    ]
  }
]

如果您使用json\u encode（$categories）将使用json格式

---

希望能有所帮助。

考虑使用演示者来擦干代码。这里有一个：