title: Edit the user via the custom method in the model
body: <p>There is a field<code>balance</code> in the user table to store its inventory. I wrote a method in the user model to increase user inventory. But I'm not sure that's correct
  I wrote this code but it does not work.What is the problem</p>
  <pre><code>public function addBalance($balance)
  {
        return $this-&gt;balance += $balance;
  }
  </code></pre>