Mapping solutions

I'm looking for a good mapping solution for a PHP project I'm working on, and wondered if any of you would be able to recommend one. Basically, I would like to be able to pass this "Map Module" several values: Latitude, longitude, map scale (e.g., 5KM x 5KM), and map resolution (500 pixels x 500 pixels), and have it return a GIF or JPEG which I can then send to the user's browser. (Additionally, it would be useful if I could pass more than one set of latitude/longitude values and have the map software display multiple points on the same map.) It seems unlikely that I could get my Host Provider to let me run third-party software like this on their servers, so I would probably have to install it on my own—which would likely end up being a Mac OS X box. Any suggestions? ...Rene