title: set expire headers through PHP
body: <p>We are rendering minified css / js through php with following expire headers</p>
  
  <pre><code>header('Expires:'.gmdate('D, d M Y H:i:s', 1407595380 + 3600 * 24 * 90).' GMT');
  header('Cache-Control: public');
  header('Last-Modified: 1407595380');
  header('Content-type: text/css');
  </code></pre>
  
  <p>Response headers we are getting mentioned in-line</p>
  
  <pre><code>Cache-Control   public
  Connection  Keep-Alive
  Content-Encoding    gzip
  Content-Length  3224
  Content-Type    text/css
  Date    Mon, 11 Aug 2014 14:54:55 GMT
  Expires Fri, 07 Nov 2014 14:43:00 GMT
  Keep-Alive  timeout=5, max=100
  Last-Modified   1407595380
  Pragma  no-cache
  Server  Apache/2.2.22 (Ubuntu)
  </code></pre>
  
  <p>But every time i refresh my page , browser gives me 200 response code instead of 304. Browser is not using own cache for php generated minified files and rest css js having 304 code on subsequent requests.</p>
  
  <p>Thanks </p>