NVP API PayPay payment processing - variable that distinguishes between products or Subscriptions
Our shopping cart uses an NVP API to process orders through PayPal. All works well for product orders. Our online business model is shifting from product to membership. We want to add 3 types of subscription memberships in addition to offering standalone products (we provide online training). This API has everything needed to blend the two types of products. The only thing I can't find out is what variable to use to let PayPal payment processing know the difference between a product order and a subscription order. This would be the cleanest way to incorporate subscriptions.
I could do this with PayPal buttons and IPN, but this is not as clean as using the already in place API.