well if you don't like the manual, check the environment variables listed by phpinfo() - HTTP_REFERER, HTTP_USER_AGENT, REMOTE_ADDR and perhaps HTTP_ACCEPT_LANGUAGE may be of some interest.
for all other information (e.g. localtime on the client's machine) I don't think you can get it, simply because this is not submitted with the http request.
does that make some sense to you?
