Developing a privateChat Application for an existing website

I have a website which can connect candidates with companies. candidates can follow companies and companies can follow candidates. I need a chat application where, a candidate can chat with a company he is following whenever the company is online. similarly, the company should be able to chat with the candidates its following whenever the candidate is online. I will provide the existing database details currently in use. using those database you must integrate the chat application by adding more tables that are required for chat into that database. You can either integrate existing free chat servers that we get online like pcpin etc or develop your own depending on your convenience. you need to show me some sample chat applications you have done before. the project needs to be completed in two days at any cost. The site is developed using php and mysql database. I dont need chat rooms. i just need individual private chat between the people just like we do in google chat and FB.