You would have to use ajax to load that content from the server again. You should look into push technology using websockets. Check out Ratchet for a php web socket, or do some research in web sockets in general.
A simpler approach would be polling, but it is kind of rough and not really as well rounded as web sockets. Polling is what came before sockets, and sockets are definitely the way to go.
There are two basic types of polling. Long polling and short polling.
Long polling is going to involve hitting the server and then the server fires a background thread which waits until it gets results, then returns the results at some time, which is when the poll fires again, and the server waits etc.
Short polling is where you hit the server once every x milliseconds, and then the server instantly responds and you deal with the response.