title: Zend update row
body: <p>I have a button, when that button is click it will update a row by +1.</p>
  
  <p>It doesn't work it only update to 1 in the database table, the next time i click it won't goes to 2, it stay at 1. I want it, everytime i click it increment the number by 1.</p>
  
  <p>Here's the funstion in model:</p>
  
  <pre><code>class Application_Model_DbTable_Row_User extends Sayka_Db_Table_Row_Abstract
  {
      public function grantDiscount()
      {
          $this-&gt;has_discount = has_discount + 1;
                  // $this-&gt;has_discount++; &lt;- not working too, only increment to 1.
          $this-&gt;save();
      }
  }
  </code></pre>
  
  <p>Controller:</p>
  
  <pre><code>if (isset($_POST['btn_buy_now']))
  {
       $user-&gt;grantDiscount();
  }
  </code></pre>