There's a note over on the PHPKitchen this morning about a new module that can by dynamically loaded into PHP giving it some mapping functionality.

The MapScript module for PHP has loads of features already, including: Generating maps on demand can be a hard job as most often you don't have the maps you need in digital form. But you can generate your own maps based on raw, digital data files which are available for free on the net. This package provides a parser for the most common format for geographical data, the Arcinfo/E00 format as well as renderers to produce images using GD or Scalable Vector Graphics (SVG).

Note: I tried the link, but I couldn't find anything on the page - maybe they pulled it back or something? At the very least, if you're looking for some good mapping software for your application, you should check out the MapServer scripts...