title: Add 10.5 seconds with DateInterval
body: <pre><code>$Datetime = $Datetime-&gt;add(new DateInterval('PT'.$secondsToAdd.'S'));
  $Datetime = $Datetime-&gt;format('Y-m-d H:i:s');
  </code></pre>
  
  <p>If $secondsToAdd is an integer everything works fine, but if it's equal to 0.5 or 10.5 it fires an error.
  Can someone help me? How can I add 10.5 seconds?</p>