Some guy wrote simple 3D rendering PHP script. It is based on well known game called Wolfenstein 3D “raycaster” algorythm and is pretty simple. Funny is that you can combine that with AJAX to get some unseen results (let’s not think about server load and traffic yet).

Here a very cool example

Other links:

3d library
Image 3D live browser rendering
Dynamic canvas demo
Creating 3D with PHP