How to create a unique ID in PHP from a long string of user info

[Zerk]

I am reading some data from a user's badge via a magnetic swipe. It brings back a long unique text string that includes the user's badge number, their name, and a few other pieces of information. I want to be able to pull up the user's information through their swipe. I was thinking of making an MD5 hash out of the user's data, but i'm not sure how unique the MD5 would be from that swipe so I can store that md5 as how I look up the user in my MySQL database?* Update: Sorry, I should add that the badge might not necessarily be from us. It might be from another company, so I really just need to take what is on the badge and create a unique ID from that.