I recently proposed PEAR::Image_3D in PEPr (the PEAR Proposal system).
Image_3D enables you to render 3D images using PHP. As I mentioned in my last post on that topic, the usage of PHP to render 3 dimensional images seems a bit ridiculous, but it definitly has a sense: Imagine the rendering of 3D charts from database data (we plan to implement a driver for PEAR::Image_Graph) or rendering of simple 3D images from user data. Of course one should not render those images on the fly, but cache them. Exciting is the fact, that rendering even complex 3D images (about 16.000 polygones) takes an acceptabel amount of time. Try it yourself! :)
Some links on Image_3D: