Make IE cache the resources but always revalidate

Question

The cache control header \"no-cache, must-revalidate, private\" allows browsers to cache the resource but forces a revalidate with conditional requests. This works as expect

Answer 1

   $last_modified = filemtime($_SERVER['SCRIPT_FILENAME']);

   session_cache_limiter(FALSE);

   header("Content-Type: text/css");
   header("Cache-Control: max-age=1, must-revalidate, private");
   header("Last-Modified: " . gmdate("D, d M Y H:i:s", $last_modified) . " GMT");

   if(isset($_SERVER["HTTP_IF_MODIFIED_SINCE"]))
   {
      if(strtotime($_SERVER["HTTP_IF_MODIFIED_SINCE"]) >= $last_modified)
      {
         header("HTTP/1.1 304 Not Modified");
         exit;
      }
   }