Is there a way to show a data stream in the web?
You can have a look at Node.JS which a sperate http server that is dedicated for streaming data using SOCKETS on HTML5 or PUSHING data with some clever JS.
It might be a learning curve with Node.JS so what I would do is set the AJAX method you are using with a repeating timer in JS. Set it to like 10 seconds interval or faster if the data is not too much. That will imitate a simple "stream"
Or you could install or do some kind of SOCKET handler in PHP and use HTML5 SOCKETS on the browser to get real live stream.
What's the program that reads the GPIO values written in? If it's PHP, then you can use JQuery and XMLHTTPRequest s to retrieve the data and render it however you want with JS. If the program is written in, say python, then you'd have to get it to write the information to a file and have the PHP script read from that when requested by the JQuery.