Build a secure online form with a small backend

I need someone to develop me a secure system for my clients to give me their credit card informations. I already have the design PSDs ready. I am open to suggestions as to how to store the credit card infos - either on the server, sent by email, added to a Google Drive sheet, etc. Clients will have to enter their invoice number, and the invoice amount will have to show when they type their . I will need a small "backend" for me to link invoice numbers and amounts. I will take care of making the transactions manually myself from the given credit card informations.