I'm going to write my own poll script in php, no problems there. But I don't want people to cheat and vote more than once. I've seen some polls that set a cookie to track that you've already voted, but that's easily defeated by not accepting cookies or clearing it. I could go by IP, but I know a lot of my visitors are behind the same proxy, so they all show the same small range of IP's.
What's the best way? Should I try something like concatenating a bunch of environment vars with the ip and match on that to detect already-voteds? That would hopefully just falsely disallow a small subset of people. Is there a better way?
