That should be up to date! (not tested)

<?php
// serve it as javascript
header("Content-Type: application/x-javascript");
// you don't want it reloading the js every time because the
// auto generated content always has a new date stamp
header("Cache-Control: max-age=604800");
header("Last-Modified: Thu, 28 Jan 2010 22:31:25 GMT");
// get the request header and search for gzip
$pos = strpos($_SERVER[HTTP_ACCEPT_ENCODING],"gzip");
// Careful here - if you do if(strpos()) then it will fail
// if gzip is the first item in the list (i.e. it's position
// in the string is zero. Instead we are checking for
// the failure to make an assignment
if ($pos === false)
{
  $js = file_get_contents("./prototype1601scriptaculous181.js");
}
else
{
  header("Content-Encoding: gzip");
  $js = file_get_contents("./prototype1601scriptaculous181.gz");
}
echo $js;
?>