Eloquent - 每位用户的最新条目

Question

我正在尝试为每个用户获取今天的最新数据库条目。

这就是我所拥有的，但它返回的是第一个条目，而不是最后一个条目。

$activity = UserJourney::where('datetime', '>', date('Y-m-d 00:00:00') )
            ->orderBy('id', 'desc')
            ->groupBy('user_id')
            ->get()
            ->keyBy('user_id')
        ; 

有什么想法吗？

由于

编辑：

这是输出：

[
{
"id": 1562,
"user_id": 10,
"datetime": "2015-02-05 11:03:41",
"url": "/",
"device": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:35.0) Gecko/20100101 Firefox/35.0",
"created_at": "2015-02-05 11:03:41",
"updated_at": "2015-02-05 11:03:41",
"deleted_at": null
},
{
"id": 1555,
"user_id": 148,
"datetime": "2015-02-05 09:20:56",
"url": "/dashboard/sales",
"device": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.94 Safari/537.36",
"created_at": "2015-02-05 09:20:56",
"updated_at": "2015-02-05 09:20:56",
"deleted_at": null
},
{
"id": 1553,
"user_id": 149,
"datetime": "2015-02-05 09:19:10",
"url": "/",
"device": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.94 Safari/537.36",
"created_at": "2015-02-05 09:19:10",
"updated_at": "2015-02-05 09:19:10",
"deleted_at": null
}
]