I'm doing an online dating website where there will be a matching service. Each user enters their profile ie hair - brown, eyes - blue etc and they also enter the characteristics for their ideal partner ie hair - brown or blonde but not red, eyes - green. The details are captured with a form and stored in the db in the users table.

For each user I want to list their matches in order of how many criteria are matched. For example, lets say there are 10 characteristics, if a user matches for only 5 of those then they would be a 50% match. So at the top of the list would be those with 100% and at the bottom those with no matches.

How would you recommend I go about writing this?