title: Adding two DateTime objects in php
body: <p>I have two <code>DateTime</code> object.<br/></p>
  
  <pre><code>$time1 = new DateTime('01:04:00');
  $time2 = new DateTime('00:13:22');
  </code></pre>
  
  <p>Addition of this two will be : <code>01:17:22</code>. How can I do it?</p>