Oh really?

To help guide the original question, in order to display the logged in users on an IRC server all that you need to do is connect to the server and send along a specially formatted command that the server understands, nothing complicated at all. There are various implementations in PHP which make talking to IRC servers easier, faster, object-oriented and so on (a Google search should suffice) or you can learn to use PHP's built-in code to do things in a more low-level way (through sockets and such like, which most of the abstractions do anyway).