Voting

Hey Guys,

I'd like to create a somewhat of a secure voting system where in a page we have about 5 to 10 pictures but in order to vote for one of the pictures you need to enter a "Voting code" once you type in your vote code you no longer can vote again.

Is there something already out there for this? If not, could someone provide a bit of guidance how to compare their "vote code" with the one in a mysql database, and making it so that number cant be used again.

thank you!