I'm not going to write you the exact code. But by psuedo code I'd do would something like this:
//req: IP.txt = IP of people that have submitted opinion already
//req: vote.txt = the tally of votes, maybe structured like
//Chocolate|20-Vanilla|23-Strawberry|38
Set up a form with several choices via radio buttons.
When click submit --> check IP.txt for if the IP has already submitted an entry and if not then add the tally to vote.txt and add IP to IP.txt.
To store in the txt files, just append for IP and grab the file, parse it, and edit the number, then re-write the whole thing.
Of course, this isn't the most secure way. If you wanted to be super anal and secure I'd use some database program such as MySQL or something to store information. But this seems fine for what your purposes are.
I'm pretty new to this whole PHP thing too, so just trying to help out where I can.
