Ignoring user cancel

Hello, I have a php process running on lighty that should continue even if the user presses cancel in his browser. The default behavior is that the web-server will kill the cgi process on user cancellation. Is there some way I can prevent the user cancel from interfering with the php process. Can I ignore the web-server's kill in php or is this a configuration that should be handled at the web-server? Any help is greatly appreciated. Thanks a lot in advance.