Legacy Codebase Modernization & Progressive Migration to PHP 8.4 / Laravel 11

Here is the English translation of your case study:

Context & Challenge

The platform relied on a large and active codebase (thousands of commits, over 1,200 classes, two large MySQL databases), accumulating technical debt over functional updates and successive major version upgrades.

The coexistence of legacy code (incomplete typing, poorly structured associative arrays) and newer modules hindered functional evolution and complicated project onboarding. The challenge was to progressively modernize the technical core to PHP 8.4 and Laravel 11 while preserving service continuity and the team's ability to ship new features.

Solution & Technical Implementation

• Tooling and Automated Refactoring (Rector & Larastan): Implementation of custom Rector rules tailored to the project and static analysis with Larastan to identify typing inconsistencies, automate repetitive transformations, and secure modifications. Gradual removal of obsolete constructs and adoption of modern PHP language features.
• Progressive Migration Strategy & Isolation: Step-by-step migration of various business components (booking engine, checkout funnel, communication services, API connectors). Validation of modifications using automated tests and fixtures, with a special focus on component compatibility and preserving existing workflows.
• Architectural Modernization (Typing & DTOs): Gradual replacement of generic associative arrays passed between application layers with typed Data Transfer Objects (DTOs), making exchange contracts more explicit and limiting manipulation errors. Cleanup of dead code and replacement of obsolete dependencies when native framework features offered a relevant alternative.
• Development Environment & CI Industrialization: Harmonization of the local environment using Docker Compose and improvement of the continuous integration pipeline to automate quality checks and non-regression tests. Optimization of test execution based on dependencies, notably distinguishing unit tests from tests requiring a MySQL environment.

Impact & Results

• Maintainability: Reduction of technical debt and improved code readability through more explicit typing, better-defined exchange contracts, and the removal of obsolete constructs.
• Reliability: Earlier detection of typing inconsistencies and regressions through static analysis and test automation.
• Scalability: Modernized technical foundation facilitating functional evolution, continuous maintenance, and the progressive onboarding of developers onto the codebase.