Dear Ben:
It´s very dangerous to send credit card numbers to email and to store credit card numbers in a database or in a file.
I think you have two good options:
- talk with a bank and they give you a script to put in your web using SSL to comunicate with them.(easy)
-again, talk with a bank and they give you a SET (SEcure Electronic Transaction) information to comunicate with them.(more difficult)
If you do that you don´t have to store any credit number and you sleep tranquil.