How to get my plug-in, wrote in php, to refresh on its own every 5 minutes?

Doing anything without a “page-load” most definitely requires Javascript because your now venturing into the A-Synchronous (AJAX) territory and JQuery is a great library to use for this stuff.

The most simple and straight forward of which is the $.post(...) method. You could then attach this send and receive AJAX call to either a shim of Javascript that uses window.setinterval() or you could just use JQuery timers. By shim I mean a well written class in Javascript or just a set of functions that are set up to detect browser versions and then use the appropriate object to instantiate. Some older browsers do not like JQuery or certain Javascript functions. If you decide on manual Javascript and XHRObjects and to handle the HTTPRequests yourself I would advise looking into which browsers support what.

Either methods will work however its nice to have something like JQuery already done for you so that you can have completely thought out code set done for cross browser compatibility as well as for going backward in browser version compatibility.

All in all I think it might look like this…

delay(function() {
    $.post("myXMLfile", function(data) {
        $('#xmlContainer').html(data);
    });
}, 4000);