actually, you don't need to use ajax to talk TO a php server.
you can make get requests using image tags, its far simpler to setup and very reliable. its a mainstay of web traffic monitors and advertisers.
example i whipped up:
value="php relay test"
var i = new Image;
var hitTime = (new Date()).getTime();
var myPhpUrl = "changeStatus.php"
i.src = myPhpUrl + "?button="+ buttonStatus + "&hitTime=" + hitTime;
you can then simply use the get/queryString features of php in your changeStatus.php (or whatever it is you are using) to catch the button parameter from the request. the example also passes the client time of the click, both for records and to guarantee a unique/uncached url for the request.