Twenty years of Zen Cart

Zen Cart started in 2003 as a fork of osCommerce. The idea was simple: keep the PHP and MySQL foundation that already worked, and make it friendlier and more flexible for the people running real shops on it. I’ve been involved since that first year, and I still lead the project today.

Twenty-plus years is a long time for any codebase. It’s a very long time for one that takes people’s money. These are the things that time has taught me.

Store owners are the users, not developers

The first real change we made was a dedicated template system. osCommerce made you edit core files to change how a shop looked, which meant every upgrade was a merge conflict waiting to happen. Giving store owners a place to put their changes, separate from our code, shaped almost every decision after that.

That principle still holds. Most people running a Zen Cart store are not PHP developers. They are shopkeepers who hired someone once, or learned just enough to get by. Every change we ship has to work for them.

Big changes are worth it, but only once

The 1.3.x series was the biggest architectural shift in the project’s history. We moved away from the tables-based layout inherited from osCommerce to a largely CSS-based design. It brought the storefront in line with modern web standards and made customisation much easier.

It was also painful. Templates had to be rebuilt, and plugin authors had to catch up. The lesson I took from it is that a platform can ask its community for one big migration every so often, and it has to be clearly worth it. Everything else should be incremental.

Backwards compatibility is the real product

A long-lived e-commerce platform isn’t just its core code. It’s the ecosystem of plugins, payment modules and custom templates that has grown up around it over two decades. Many of those were written by people who have long since moved on, and they are still running in production shops.

So backwards compatibility is not a nice-to-have. It is often the single biggest constraint on every design decision. Before we change a function signature, rename a hook or remove a global, we have to ask how many stores it will quietly break, and whether the owner will even know why.

PHP keeps moving, and so must we

The PHP that Zen Cart was born on is almost unrecognisable next to PHP today. Each major release brings deprecations, stricter typing and removed features. Hosting companies upgrade on their own schedule, and store owners find out when their checkout stops working.

Keeping up with PHP versions is a large and unglamorous part of maintaining the project. It is also one of the most valuable things we do. A platform that can’t run on a supported PHP version isn’t safe to run at all.

Security is a permanent job

When your software handles orders and payments, security isn’t a feature you finish. Over the years that has meant hardening against CSRF, keeping card data out of scope with hosted payment flows, and responding quickly when an issue is reported.

Privacy has become part of that job too. Tools like zencart-gdpr-dsar exist because store owners now need to handle data export and erasure requests properly, with an audit trail, and most of them can’t build that themselves.

The community needs somewhere to live

Open source runs on people helping each other, and that needs a home. For years the Zen Cart support forum ran on vBulletin, tied to an old PHP version, slow, and hard to search. We eventually rebuilt the support site from scratch in Laravel, with a proper CMS for guides and a permission system designed around how the forums actually work.

It was a reminder that the infrastructure around an open-source project matters as much as the code. If people can’t find answers, they leave.

AI changes how people learn a codebase

The newest chapter is AI-assisted development. A codebase with twenty years of history has a lot of conventions that are obvious to long-time contributors and invisible to everyone else, human or machine.

That’s why I built zencart-ai-assist. It makes the Zen Cart docs and code searchable locally and exposes them to editors and coding agents through an MCP server. The goal is to help new developers, and the tools they use, understand how Zen Cart expects things to be done before they start changing it.

Why keep going

Zen Cart is released under the GPL and remains free. Official development has slowed over the years, but a community of developers keeps the platform current with plugins, fixes and support. There are still people running businesses on it every day.

That’s the reason to keep going. Somebody’s shop depends on this code working tomorrow, and on the next PHP release after that.