title: Using sum() sql with php ActiveRecord
body: <p>I'm using <a href="http://phpactiverecord.org/" rel="nofollow">ActiveRecord</a> in my app. I need to add many objects by attribute. Currently I do it as follows:</p>
  
  <pre><code>foreach($objects as $object):
      $result += $object-&gt;value;
  endforeach;
  </code></pre>
  
  <p>But it is very slow. I think I could get the same result but more efficient by sql sum(), so de question is can ActiveRecord return me the sum() result?</p>