Legacy PHP to Laravel Blueprint

What and Why

Legacy PHP applications, whether hand-rolled procedural scripts or aging frameworks like CodeIgniter, typically mix SQL, HTML, and business logic in single files and often run on unsupported PHP versions. This blueprint restructures them into Laravel, gaining a clear MVC structure, the Eloquent ORM, Composer dependency management, and modern PHP 8 typing, attributes, and security defaults. Laravel is a widely-adopted, actively maintained PHP framework, so the move also restores a supported foundation and a large library ecosystem.

Phases

Assessment. Inventory entry-point scripts, raw SQL queries, global state, and inline HTML. Determine the current PHP version and flag the SQL-injection and cross-site-scripting (XSS) prone code, which is endemic in legacy PHP. Map the URLs the application serves today, since those are the contract that must be preserved through the migration.

Scaffolding. Create a Laravel project alongside the legacy application. Configure Composer for dependencies, environment-based configuration per twelve-factor principles, and a front controller that can route some paths to Laravel and pass the rest through to the legacy code during transition.

Routing migration. Move pages one at a time. Define Laravel routes and controllers, convert inline SQL to Eloquent models or the query builder (both of which parameterize queries and thereby close injection holes by default), and move markup into Blade templates, whose automatic output escaping prevents most XSS.

Data layer migration. Introduce Laravel migrations to version the database schema, replacing the ad-hoc, untracked database changes legacy apps usually rely on. Keep the existing database in place; Eloquent maps onto the current tables, so no data move is required.

Cutover. Use the strangler fig pattern at the front controller to shift each route to Laravel once it is verified, then retire the legacy entry points after the last path is migrated.

Key Risks and Mitigations

• Security vulnerabilities: Legacy PHP commonly contains injection and XSS flaws. Eloquent and Blade close many by default, but verify with static analysis (SAST) and prioritize internet-facing pages first so the riskiest code is hardened earliest.
• Downtime: Migrate page by page behind the front controller rather than switching the entire application at once, keeping rollback trivial.
• Skills gap: Developers must learn Laravel conventions, the service container, and modern PHP typing. Pair on the first routes so the patterns spread before scaling out.

Recommended Tooling

Laravel with Eloquent and Blade, Composer for dependency management, MySQL as the existing datastore, Redis for caching and session storage, and a SAST scanner in CI to enforce the security baseline.

Success Metrics

Track lead time and deployment frequency for web changes, which improve with a structured framework, and defect rate, especially security defects, which should fall as parameterized queries and automatic escaping replace ad-hoc string handling.

Prerequisites

Full source for the legacy application, a record of current URLs to preserve, a supported PHP runtime, and manual or automated tests per page to verify parity.

Sequencing and Rollback

The front controller is the rollback point: any route can be directed back to the legacy code path with a routing change, with no data impact since the database is shared. Sequence routes by security exposure, migrating internet-facing pages with injection or XSS risk first. Run the legacy and Laravel paths side by side and compare output per page before retiring the legacy entry point. Keep migrations additive during transition so the schema stays compatible with both code paths until the legacy app is fully retired. Confirm a staging environment runs the Laravel routes against a copy of production data so Eloquent's mapping onto the existing schema is validated for every migrated page before that page is exposed to real users.