Local coupons and deals marketplace with split seller payments

The challenge

A US start-up wanted to launch a local deals marketplace. Businesses would sign up as sellers and publish coupons and deals alongside ordinary products and services, and shoppers would find offers near them. A standard multi-seller store covered the seller accounts, but not coupons, seller membership plans, seller media, payments split between several sellers, or tax handling.

The client had a long roadmap, so the work was organised into stages and numbered modules, with the requirements tracked in shared specification documents and module lists. Because the platform's core files had to be modified to support the model, every new module also had to fit cleanly into an increasingly customised codebase.

What we did

• Marketplace foundation. We supplied our own multi-seller extension, set up a demo and test server, and customised the extension for coupons and services, including renaming stores to sellers throughout.
• Coupon module (Stage 1). We built a coupon and deals module that works with the multi-seller layer, including a Popular Coupons block, and fixed issues such as a discount being lost after logout.
• Stage 2 and numbered modules. We delivered seller membership plans, seller image and video galleries with admin approval and removal controls, and a series of further modules (M1 to M6) from the client's specification.
• Split seller payments. For module M7 we implemented PayPal Adaptive parallel payments in an iframe, so a single checkout pays several sellers at once. Module M9 added tax options on the customer side.
• Fixes and security. We fixed cart bugs, a Google Maps API key problem and seller video playback, and later removed backdoor files that were causing redirects, returning a clean copy of the site.
• Dedicated developer. From 2018 we provided a developer on a weekly basis, working through the client's prioritised task lists.

Tech stack

PHP, MySQL, OpenCart 1.5, PayPal Adaptive Payments, Google Maps API