select sum column and group by with Mongodb and Laravel
<p>I have a issue with my query:</p>

<p><a href="https://i.stack.imgur.com/JQcp7.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/JQcp7.png" alt="enter image description here"></a></p>

<p>I want to </p>

<blockquote>
  <p>SELECT "user_info" with SUM "amount" and GROUP BY "user_id"</p>
</blockquote>

<p>I am using Laravel 5 and <strong><em>jenssegers/laravel-mongodb</em></strong></p>

<p>Thank you so much.</p>