Delivering a Unique Message from a Database of Messages

[shakingspear]

I have an idea for a website where, after signing up, each user is given a unique writing prompt. Each prompt from the database should only be used once and never given again. I think this can be done either as an email auto response or on the website itself. Would one of these options be better than the other? If so, could you point me in the right direction to learn more about how to do this?

Thank you very much for your help.

[gnomeontherun]

Well if they should never be reused, perhaps it would make more sense to just create a random string using PHP or something?