script won't work on other server

I have a small script that I am testing out on two different servers. It uses the $_SERVER['HTTP_USER_AGENT'] to detect the browser and serve up a style sheet dependent on the results. (Please don't comment on its usefulness, it's just an example.) On one server, I can get this script to run correctly in all browsers that I test. On another server, it will not run correctly in Netscape (testing for the word Gecko, but have used Netscape also). Any help would be appreciated. Link to script: http://www.asrm.org/class/php/angelia.php In case it's needed, link to file with phpinfo(): http://www.asrm.org/test/test.php