learn eloquent query.

test_get_count_of_post_comment

$posts = Post::leftJoin('comments', 'comments.post_id', '=', 'posts.id')
    ->selectRaw(
        'posts.*,
        count(comments.id) as comments_count'
    )
    ->groupBy('posts.id')
    ->orderBy('comments_count', 'desc')
    ->get();