title: Incrementing Cakephp database field by a value
body: <p>I have this field whose value i have to increment the field value by a specific value.
  I am using this </p>
  
  <pre><code>$data['quantity']     = 'Order.quantity+1';
  </code></pre>
  
  <p>which doesnt works for me quantity is a integer coloumn here.
  Also will it work when nothing is in database?.</p>
  
  <p>Regards
  Himanshu Sharma</p>