I need to find the screen resolution of a users screen who visits my website?
The quick answer is no, then you are probably asking why can't I do that with php. OK here is a longer answer. PHP is a serverside scripting language and therefor has nothing to do with the type of a specific client. Then you might ask "why can I then get the browser agent from php?", thats because that information is sent with the initial HTTP headers upon request to the server. So if you want client information that's not sent with the HTTP header you must you a client scripting language like javascript.