title: How do I subtract time in PHP?
body: <p>So, I have the following being returned by an API:</p>
  
  <pre><code>&lt;startTime&gt;2011-04-12T01:28:40.000Z&lt;/startTime&gt;
  </code></pre>
  
  <p>It's in UTC/Zulu format. How would I go about getting the time elapsed (in seconds) since that timestamp in PHP?</p>
  
  <p>Thanks for any pointers!</p>