Make a lightweight chatroom for my website (ajax and/or php)

This project is for an ADULT website... You will need to do 1 things in that project: 1)Add a php chatroom to the [login to view URL] chatroom need to accept any visitor and they can also connect with their facebook /other social [login to view URL] they first connect,they choose a name and their [login to view URL] registered member of the website have their avatar and their username in a different color that the other users on the [login to view URL] on the chat can start a private a private conversation with another person by clicking on his/her name.(This chat absolutely need to be seemless integrated to the website style and use very little server ressource...)