Send user to page

Hi firstly thanks for taking the time to look at this.

In my application a user is able to create a chatroom and add friends to the chat room ( already complete)

However I want the user to be greeted with a alert box saying "User X has invited you to chatroom Y" with the options "Accept", "Decline". If the user accepts then I want a new page to open which displays the chatroom they were invited to. My chatrooms are represented with roomids in a mysql database.

Could anyone give me any hints on how I might do this ?

Thanks