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PHP monolith → React/Next.js

A web agency had an e-commerce client with an old PHP backend – and no React developer on the team. Five weeks later a modern frontend sat in front of it, without rewriting the backend.

The problem

The backend was a grown PHP monolith – no framework, no tests, barely maintainable. At the same time the end client wanted a modern, fast frontend. The agency owned the client relationship and the project management, but had no React expertise. A complete backend rewrite would have blown the budget and the timeline.

The solution

I was hired as a subcontractor and built a React/Next.js frontend with TypeScript in front of the existing PHP API – including state management, responsive design and deployment. The backend was left untouched and the agency remained the single point of contact for its client.

Step-by-step approach

• Analysing the PHP endpointsExisting API routes, data formats and error cases mapped – without touching the production system.
• Frontend architecture & prototypeNext.js project structure, routing and TypeScript types defined for every API response.
• API connectorCleanly encapsulated data access layer including error handling, caching and loading states.
• UI implementationComponent-based interfaces, responsive layout and performance optimization.
• Deployment & handoverBuild pipeline, hosting setup and documented handover to the agency – including a short training session.