What do I need to research to make php setup a specific user only chatroom?

[ubercakes]

I'm creating a social network for a friend and I need to make a flash webcam to talk to another flash webcam. I have all the flash code working, now all I need is a way to let users match themselves up to each other without other users being able to barge in. What areas of php do I need to learn about to do this?

 

Dallas.