I’ve got a client who wants to be able to accept memberships online (their site is built on MODx 9.6.1). They are already using Securenet for their payment processing (for other things, on a different site) and want to use it for the membership fees and for contributions on their main site.
Securenet tells me they recommend OSCommerce as a shopping cart for PHP. They sent me a 14-page document explaining implementation (Securenet Regular HTTPS POST API). Ay yi yi...
I’m killer at integrating PayPal, but this may be way over my head...I think

. Is this simpler than they make out? Or is this a job that needs to be shopped out in the code geek world?
Any suggestions/assistance very welcome indeed! Many thanks.