Hi, I was wondering if anyone could help me on this or atlest where to began and what would it all end tail

I have a small LAN at my house and I honestly want to start programing in PHP. Me and my friends love to play MUDs but want to do one where we control it. My Question and thought is... How in the world would we create a MUD in PHP. I know it would take a lot, but i don't know how much. And since i can't find one online i'm thinking this would be the first MUD. I figure I might have to use something like AJAXs if not AJAX itself for at lest some kind of gui but i want this to run on a web page. If anyone has any clue on how to star this that would be great