Hey Rathji,
What your describing is a 'lightbox' solution. Much like this:
http://www.lokeshdhakar.com/projects/lightbox2/
It typically runs on JS and doesn't need PHP to run, but obviously can be used in conjunction with PHP/ASP if you need. But that's more for dynamic websites.
There's been quite a few 'lightbox' type plugins created for many different javascript libraries (jQuery/Prototype/MooTools) such as these:
http://www.designyourway.net/blog/re...htbox-plugins/
Personally I recommend finding one that runs on jQuery over prototype, I quite like
http://fancybox.net/ (although there site seems to be down right now).
Setting them up is ussually pretty easy, you include the JS & CSS files in the header, activate the script & attach a custom class or rel to the links you want to trigger the lightbox with.
tl;dr: Use This:
http://www.lokeshdhakar.com/projects/lightbox2/