PHP backend case study

Legacy PHP Refactoring Lab

Refactoring lab for improving legacy PHP through behavior protection, service extraction, safer structure, and incremental modernization.

Discuss a similar problem Back to projects

Case study

Technical scope

Some repositories are private until the work is closed. Project scope, technical decisions, and operating scenarios are described on the page. I can discuss the code during a technical conversation.

Problem

Legacy PHP rarely allows safe big-bang rewrites because it is unclear which behaviors are accidental and which are part of the system contract.
The project shows a small-step strategy: freeze behavior first, extract a service next, then improve structure.

Technical decision

Characterization first, small seams, incremental cleanup.
legacy/ remains as the starting point so refactoring can be compared against original behavior.
src/Application is the target location for application services extracted from procedural code.
docs/ADR-001-refactoring-strategy.md acts as guardrails, while phpstan.neon is the entrypoint for gradually increasing quality strictness.

Result

Refactoring steps and behavior protection.
Scaffold with legacy/, src/Application, tests/Characterization, ADR guardrails, and phpstan.neon.
Defined first milestone for behavior-locking tests and extracting one application service.
Preparation for DTO, validation, and gradual static-analysis level increases.

Stack

Legacy / PHP / Refactor / Tests
composer install
composer test