如何使用主键和辅助键对数组元素进行分组？

Question

我有这个数组：

Array
(
    [0] => Array
        (
            [id]=>1
            [account_id] => 1
            [object_id] => 43
            [object_type] => PHOTO
            [action_type] => UPLOAD_PHOTO
        )

    [1] => Array
        (
            [id] => 1
            [account_id] => 1
            [object_id] => 42
            [object_type] => PHOTO
            [action_type] => UPLOAD_PHOTO
        )

    [2] => Array
        (
            [id] => 1
            [account_id] => 1
            [object_id] => 41
            [object_type] => PHOTO
            [action_type] => UPLOAD_PHOTO
        )

    [3] => Array
        (
            [id] => 2
            [account_id] => 2
            [object_id] => 1
            [object_type] => USER
            [action_type] => FOLLOW_USER
        )

    [4] => Array
        (
            [id] => 1
            [account_id] => 1
            [object_id] => 2
            [object_type] => USER
            [action_type] => FOLLOW_USER
        )

    [5] => Array
        (
            [id] => 1
            [account_id] => 1
            [object_id] => 1
            [object_type] => PHOTO
            [action_type] => UPLOAD_PHOTO
        )

)

现在我想通过 id 作为主键和 action_type 将具有相同值（例如 UPLOAD_PHOTO）的元素分组为辅助键，例如：

Array
(
    [0] => Array(
        [id] => 1
        [account_id] => 1
        [actions] => array(
          [1] => array(
              [object_id] => 42
              [object_type] => PHOTO
              [action_type] => UPLOAD_PHOTO
           )
          [2] => array(
              [object_id] => 43
              [object_type] => PHOTO
              [action_type] => UPLOAD_PHOTO
           )
         )      

 ) 
[2] => Array
    (
        [id] => 1
        [account_id] => 1
        [actions] = array(
            [0] => Array
             (
               [object_id] => 3
               [object_type] => USER
               [action_type] => FOLLOW_USER
             )
            [1] => Array
             (
               [object_id] => 4
               [object_type] => USER
               [action_type] => FOLLOW_USER
             )

        )

    )

)

我尝试了一些解决方案但没有成功。

Answer 1

构建输出数组时，您需要使用有意义的数组键。这样您就可以找到需要添加 in 元素的 out 元素：

$in = (...your array...);
$out = array();

foreach($in as $element) {
   $id = $element['id'];
   //If that id hasn't been seen yet, create the out element.
   if (!isset($out[$id])) {
       $out[$id] = array(
           'id'=>$element['id'],
           'account_id' => $element['account_id'],
           'actions' => array()
       );
   }

   //Add that action to the out element
   $out[$id]['actions'][] = array(
       'object_id' => $element['object_id'],
       'object_type' => $element['object_type'],
       'action_type' => $element['action_type']
   );
}

---

我不确定为什么您的输入元素具有不同的字段...如果这是一个所需的功能，其中一组可能的字段属于 id组和另一个集合属于该操作，您可以这样做（可读性稍差，但更灵活）：

$in = (...your array...);
$out = array();
//These define which fields from an 
//input element belong to the id,
//and which to the action.
$id_fields = array_flip(array('id','account_id','object_user_id');
$action_fields = array_flip(array('object_id','object_type','action_type');

foreach($in as $element) {
   $id = $element['id'];
   //If that id hasn't been seen yet, create the out element.
   if (!isset($out[$id])) {
       $out[$id] = array_intersect_key($element, $id_fields);
       $out[$id]['actions'] = array();
   }

   //Add that action to the out element
   $out[$id]['actions'][] = array_intersect_key($element, $action_fields);
}

如果输入元素可以不同，这是一个更好的解决方案，因为如果预期字段（'id 除外） ') 丢失，脚本会处理它 容易地。