Where can I get a script for use of generating promo codes?

I want a script that I can use for my website, I will offer promotions, reveal a code every hour or so, and the user has to go to a redeem code page and redeem it. Does anybody no where I can get a script like this?

 

just create a script that will create a random codes

 

create random code and save it to sql database (as a valid promo code) and update it as invalid once used