My instruction here is for PHP/ X-Cart developer only. Some businesses may already have customer credit card information thru AuthorizeNet CIM system. All you’ll do is adding some files and functions to charge the existing credit card instead of asking customers to enter credit card information again on every purchase.

Here’re some steps to follow to integrate CIM in your X-Cart.
Step 1: Register with AuthorizeNet the CIM feature. It may cost a little monthly fee by Authorize.Net.

Step 2: FTP to your server. Go to X-Cart root directory. Look for these files

payment/payment_offline.php
include/cart_process.php =>check if user has credit card on file by

Step 3: Create a new file and write some new functions to charge customers from their existing credit cards. Remember, it’s illegal to store customer credit card number in your database. You must use AuthorizeNet CIM to store credit card information. Then AuthorizeNet will return a Profile IDs for next time usage:

New file: /payment/cc_authorizement_cim.php
function charge_existing_creditcard()
function func_get_ccard_type()
function get_authnet_payment_profile_id()

Step 4: Follow instruction to integrate with AuthorizeNet CIM payment method.

Step 5: Add a new payment called “AuthorizeNet CIM” and activate it thru X-Cart Store Admin interface. Check the Activate button for this payment method.