Creating a popup window can be done using JS.
However, you cant remotely control that popup window from some control panel, at least not under normal circumstances.
You could write a program that allows this sort of control, I suppose, but very likely it will be deemed as a malicious program, acting as a trojan.
However, do you mean create a popup that the user can close from his/her own control panel?
That should be easy enough, again using JS or some other clientside scripting language, not PHP.
