title: PHP Last-Modified header not sent?
body: <p>So I have this at the very top of my PHP file:</p>
  
  <pre><code>&lt;?php
  // Set headers
  header('Content-Type: text/html; charset=UTF-8');
  header('Content-Style-Type: text/css');
  header('Content-Script-Type: application/javascript');
  header('HTTP/1.1 200 OK');
  header('Content-language: en-US');
  header('X-Powered-By: ');
  header_remove('X-Powered-By');
  header('Last-Modified: Tue, 01 Jan 2013 00:00:00 GMT');
  header('Cache-Control: no-store, no-cache, max-age=0, must-revalidate');
  header('Pragma: no-store, no-cache, max-age=0, must-revalidate');
  header('Expires: Tue, 01 Jan 2013 00:00:00 GMT');
  ?&gt;
  </code></pre>
  
  <p>So when I check the Firefox console's NET tab on my site's URL I don't see the Last-Modified header. Any suggestions?</p>