php递归生成无限极树状数组

在生成多级树状数组之前，我们一般得到的数据结构如下

[{
    "id": 6,
    "parent_id": 5,
    "name": "体育专题1",
    "intro": "体育专题1111介绍",
}, {
    "id": 5,
    "parent_id": 4,
    "name": "体育专题",
    "intro": "体育专题介绍",
}, {
    "id": 4,
    "parent_id": 0,
    "name": "体育",
    "intro": "体育所有区块",
}, {
    "id": 3,
    "parent_id": 1,
    "name": "最视频",
    "intro": "最视频介绍",
}, {
    "id": 2,
    "parent_id": 1,
    "name": "轮播台",
    "intro": "首页轮播台介绍",
}, {
    "id": 1,
    "parent_id": 0,
    "name": "首页",
    "intro": "首页的所有区块",
}]

我们需要根据其中的pid（parent_id）与id之间的关系，来将数数组转成多级数组
首先考虑，如果使用递归，递归执行的条件是什么？或者反过来说，递归返回的条件是什么？
假设我们用上述数据的第一个元素pid是5，继续找到id为5的数据找到第二个元素，第二个元素pid为4，继续找id为4的元素，id为4的元素pid为0，说明找到了最后
所以代码如下

  $newData = $this->digui($data,0);
  function digui($arr, $pid = 0)
    {
        $newArr = [];
        foreach ($arr as $item) {
            if ($pid == $item['parent_id']) {
                $item['children'] = digui($arr, $item['id']);
                $newArr [] = $item;
            }

        }
        return $newArr;
    }

$newData = $this->digui($data,0);传入的data中的元素，而其中的递归相当于找出当前被遍历元素的所有后代元素（包括儿子元素孙子元素）。所以最后我们得到的数据结构如下

[{
    "id": 4,
    "parent_id": 0,
    "name": "体育",
    "intro": "体育所有区块",
    "created_at": 0,
    "updated_at": 0,
    "children": [{
        "id": 7,
        "parent_id": 4,
        "name": "体育专题2",
        "intro": "体育专题22222介绍",
        "created_at": 0,
        "updated_at": 0,
        "children": []
    }, {
        "id": 5,
        "parent_id": 4,
        "name": "体育专题1",
        "intro": "体育专题介绍",
        "created_at": 0,
        "updated_at": 0,
        "children": [{
            "id": 6,
            "parent_id": 5,
            "name": "体育专题1-1",
            "intro": "体育专题1111介绍",
            "created_at": 0,
            "updated_at": 0,
            "children": []
        }]
    }]
}, {
    "id": 1,
    "parent_id": 0,
    "name": "首页",
    "intro": "首页的所有区块",
    "created_at": 0,
    "updated_at": 0,
    "children": [{
        "id": 3,
        "parent_id": 1,
        "name": "最视频",
        "intro": "最视频介绍",
        "created_at": 0,
        "updated_at": 0,
        "children": []
    }, {
        "id": 2,
        "parent_id": 1,
        "name": "轮播台",
        "intro": "首页轮播台介绍",
        "created_at": 0,
        "updated_at": 0,
        "children": []
    }]
}]