laravel使用加载进行优化
两种方式：
1.使用：with
$posts=Post::orderby('created_at','desc')->withCount(['comments','zans'])->with('user')->paginate(5);
2.使用：load
$posts=Post::orderby('created_at','desc')->withCount(['comments','zans'])->paginate(5);
$posts->load('user');