When you say you are a newbie at PHP, does this mean you are also a newbie at programming in general, or do you have some other programming experience in other languages? Do you know anything about database design and SQL?
If, in fact, programming and databases are new to you, I would suggest stepping back a bit and first concentrate on learning the basics. If you just jump into the deep end without at least learning to dog paddle, then you may find yourself drowning in the multitude of issues you'll need to address in the development of an on-line multi-player game -- it is not a trivial application that you'll just want to throw together and will probably take many thousands of lines of code.
I would suggest that you first get hold of an introductory book on learning PHP and MySQL and work your way through it. While doing that, spend a bit of time thinking about the game you want to build, and try to break it down into many separate, small pieces of functionality (the smaller the chunks, the better). Then pick one piece that you want to try to implement, and start applying your recently gained programming/database knowledge and also looking for tutorials specific to that narrowly focused need. You may also be able to find existing scripts for those specific functions that you can plug right in, or use with minor modifications.
