<?php
function cache_check($mtime)
{
   if (DEBUG)
    var_dump($_SERVER);

  $HTTP_IF_MODIFIED_SINCE=$_SERVER['HTTP_IF_MODIFIED_SINCE'];
  $if_modified_since = preg_replace('/;.*$/', '', $HTTP_IF_MODIFIED_SINCE);

  $gmdate_mod = gmdate('D, d M Y H:i:s', $mtime) . ' GMT';

  if ($if_modified_since == $gmdate_mod) {
    header("HTTP/1.0 304 Not Modified");
    exit;
  }
  header("Last-Modified: $gmdate_mod");
}
?>