img = new Image();
img.src = 'process.php?height=' + screen.height + '&width=' + screen.width;
img = undefined;
That runs process.php on the server passing it the width and height of the screen that the browser is displayed on.
Most scripts would use a lot more code than that because most people don't realise that if you are just sending data from the web page to the server and don't need a response back that you can do it this way and only need three lines of code to pass as much information to the server as needed.