How to select year and month from the created_at attributes of database table in laravel 5.1?

My problem is that I want to get data form the database table from the created_at attributes as per year and month only. The code I have tried is:

$post= Mjblog::select(DB::raw('YEAR(created_at) year, MONTH(created_at) month'));
$posts_by_y_m = $post->where('created_at',$post)->get();

via Chebli Mohamed