If you’re looking for a simple way to add charts and graphs with PHP you might want to check out PHP/SWF Charts. It’s a stupid-easy to use Flash based system that receives data from PHP includes.

There’s a free version with slightly limited features, but a full-featured single license is only $45 and it’s good for one domain name and all its sub-domains.

I prefer PHP/SWF Charts over alternatives like JpGraph.