Create Web Chat Application

I need to code a chat web app, but I want to see how someone else will do it, so I can learn from it after. I'm familiar with PHP, but it can be in anything, as long as it works well in browser. It needs to be just like this... Basic Web Chat SIte/Application - User can send a message up to 200 characters (there will be an input box and a buttons) - Display the last 10 messages people have posted - Button to load next 10 older messages (must communicate with server, but must not refresh the page) - Each message sent should also show the user's IP no., and date/time sent - Login system preferable (with option to post as a guest) Mock Up Attached Thanks