PHP being server side, you can't automatically have a message pop up to notify someone that a message has been received.
That being said, you can check to see if there are new messages received when a new page or the current page is refreshed.
A good way to check every 2 minutes is to use a meta refresh.
I'm sure there would be an application writen somewhere. But if contract work is what you are interested in write me an email, I could give you a quote from the information provided.
Alternatively I sugest learning php, and mysql. You'll get a really warm fuzzy feeling inside once you get your application working. 😃