Dynamically show full-sized images on thumbnail mouseover in PHP

I开发者_StackOverflow中文版 want to show an image when I mouse over a thumbnail, like this website does. How can I do this, in PHP?

use frontend as jquery/javascript -> onmouseover -> ajax to server to fetch full size image -> successful return -> show image in modal box or something..

or instead of re-inventing the wheel, you could look at the following too : http://www.ajaxrain.com/tag?tag=Tooltips
http://www.huddletogether.com/projects/lightbox2/