Refresh DIV using AJAX, very simple project!

Hello, first of all this is a very simple project for someone that has already done this! I am a developer myself and I am working on a project. I have a single Div that I need to refresh on button click using AJAX. once the button is refreshed, the Div has to refresh and display the new content for all users at the same time. a few milli seconds is ok too. but it has to be updated for all users. I looked at Node.js option too but that is a bit far fetched. what you'll do: ignore everything i.e. the div contents etc, and just refresh the Div so the new contents will be displayed inside it Once a button is pressed. thats all. Please do not bid if you don't know what you are doing as i have already wasted a few days trying to work this out. This should only take 1 hour at most for anyone who knows what they are doing. again, 1 hour at most. my code is not big and its only 1 php page that you need to concentrate on. Simples. Thanks