PHP Graphing Library
I recently did search for an open source PHP graphing library. Besides the well known but non-free JpGraph library, I found many simple ones either for bar graphs or pie graphs. Until I stumbled across Zack Bloom's Advanced Graphing Class. It does pie, line and bar graphs including function plotting and has a plethora of options to set. Most notably is it's ability to autoscale graphs depending on the input data.