<?

function outputetag($page){
  $length=strlen($page);
  $etag = md5($page);
  header('ETag: '.$etag);

  if(isset($GLOBALS['HTTP_SERVER_VARS']['HTTP_IF_NONE_MATCH'])){
    $inm = explode(',', $GLOBALS['HTTP_SERVER_VARS']['HTTP_IF_NONE_MATCH']);
    foreach($inm as $i){
      if(trim($i) == $etag){
        header('HTTP/1.0 304 Not Modified');
        return;
      }
    }
  }
  if(extension_loaded('zlib') && $length>1024 && isset($GLOBALS['HTTP_SERVER_VARS']['HTTP_ACCEPT_ENCODING'])){
    $ae = explode(',', str_replace(' ', '', $GLOBALS['HTTP_SERVER_VARS']['HTTP_ACCEPT_ENCODING']));
    $enc = false;
    if(in_array('gzip', $ae)){
      $enc='gzip';
    }elseif(in_array('x-gzip', $ae)){
      $enc='x-gzip';
    }
    if($enc){
      $page = gzencode($page);
      $length = strlen($page);
      header('Content-Encoding: '.$enc);
      header('Vary: Accept-Encoding');
    }
  }
  header('Content-Length: '.$length);
  return $page;
}

ob_start('outputetag');

?>