In recent versions of PHP, php.exe is only suitable for running from the command line. It does not register GET, POST or cookie variabeles. You must configure the PHP plugin to use php-cgi.exe!
WWW Server caches files, and PHP pages are no exception. So do not forget to empty the cache after you changed a script. Or, if your script is really dynamic, set the appropriate HTTP headers:
header("Pragma: no-cache"); header("Cache-Control: no-cache");