PHP based online survey tool

Hello All, I am looking to develop an online survey for a non-profit. The user should be able to complete the survey and see the results in the form of a visualization (i.e. pie chart) upon completion. I found this tool (http://www.iscripts.com/survey/) but not sure how good it is. Does anyone have any suggestions for PHP based online survey tools? Any suggestions would be greatly appreciated. Thank you all in advance. Best, Christopher This message is for the designated recipient only and may contain privileged, proprietary, or otherwise private information. If you have received it in error, please notify the sender immediately and delete the original. Any other use of the email by you is prohibited.