UPDATED FOR CLARIFICATION
I've got this rating plugin that keeps submitting & duplicating the rating data on page refresh. When a user wants to add a rating, they have to click a button that takes them to "mysite.com/?review=true"
After they submit their review, the browser stays on "mysite.com/?review=true"
Upon refreshing the browser, the review is resubmitted, causing duplicate entries.
How can I check against duplicates in the database and stop this?
http://pastebin.com/c6wPGRD5 - class.php
http://pastebin.com/tz4PvWtS - form submit.php
http://pastebin.com/9ebCxpMZ - plugin.php