Update Website Program Using PHP7

I own a website that gives people the ability to rent audio books by mail by signing up to a membership plan. I have just updated the Front End pages which are being held in a testing area. I am in need of some assistance revising the back-end program to connect with the new pages. The website is www.TalkingBooksPlus.com. This is a custom built website using PHP7. There are 3 parts to what I am looking for: A - Connecting Customer Information from the Front End to Bank End using [login to view URL] as the Payment Gateway. Then Create a Front End Customer Record based on the response from [login to view URL] 1. Update the system to process payments using the information from the NEW page ([login to view URL]) and send it to Authorize.net. The program should already have how to create a record for Authorize.net. 2. Once [login to view URL] comes back with confirmation that the customers credit card is valid. The system needs to create a Unique Customer Record and a New Page confirming the USERNAME, PASSWORD and All Customer Information should appear back to the customer. The customer information then needs to be held in the Customer Database. If there is a problem with the credit card or member information that prevents [login to view URL] from validation, the system should not create record but provide an error message that appears from Authorize.net. B- Revise Email System to Send Out Customer Emails based on New Customer Information Page. C - Delete All Books Currently Being Held in the 50% Off! Category from the database.