generating charts/graphics

I'm working on (actually I'm almost finished) on a very nice ad management system. It has a script that generates a very informative report, in HTML. But I wanted something more... like some comparative chart... or pie chart... can anyone give some hints, where can I find info on this? Is this easy to do in PHP? Can I get something already implemented? Some class or something? thanks... _____________________________ . Christian Dechery . . Gaita-L Owner / Web Developer . . http://www.webstyle.com.br . . http://www.tanamesa.com.br