Random Image Problem

I followed the PHP tutorial (http://www.kirupa.com/web/random_image.php) to the letter and it doesnt seem to work for me. Instead of a new image popping up I have the same 2 images side by side when I refresh the page. This is really odd as I have only inserted 1 image in the page. Any ideas anyone?
this is what i mean (http://www.adamstrainor.com/random.php)