Create payment gateway in simple php script

Hello i need create a payment gateway for my php website, when user add your crefit card/iban data i need automatic debit the invoice.

See this my example:
www.nedate.com

Users for test:

1:
Username: user1
Password: user1

2:
Username: user2
Password: user2

3:
Username: user3
Password: user3

Admin page:
Username: admin
Password: admin