title: Cache control and expires header for PHP
body: <p>I'm setting my headers </p>
  
  <pre><code>$offset = 60 * 15;
  
  header("Expires: " . gmdate("D, d M Y H:i:s", time() + $offset) . " GMT");
  header("Cache-Control: max-age=$offset, must-revalidate"); 
  </code></pre>
  
  <p>However when running FireBug its giving me the following header information </p>
  
  <pre><code>HTTP/1.1 200 OK
  Date: Mon, 25 Jul 2011 12:15:12 GMT
  Server: Apache/2.2.11 (Win32) DAV/2 mod_ssl/2.2.11 OpenSSL/0.9.8i PHP/5.2.9
  X-Powered-By: PHP/5.2.9
  Expires: Sat, 01 Jan 2000 00:00:01 GMT
  Cache-Control: post-check=0, pre-check=0, max-age=0
  Pragma: no-cache
  Last-Modified: Mon, 25 Jul 2011 12:15:13 GMT
  Keep-Alive: timeout=5, max=100
  Connection: Keep-Alive
  Transfer-Encoding: chunked
  Content-Type: text/html
  </code></pre>
  
  <p>Anyone know why my headers aren't being recognised? </p>