Symfony 4.1

Symfony 4.1 was a feature release built on the Symfony 4.0 codebase. It introduced the Messenger component for routing application messages to handlers, including transport-backed asynchronous processing, and added cache tag invalidation support through the TagAwareAdapter. The release also added and refined framework, security, form, console, dependency-injection, and developer-tooling capabilities while beginning deprecation paths for APIs changed or removed by later Symfony releases.

Symfony 4.1 has reached end of life. Its maintainers no longer provide fixes for newly discovered security issues, defects, or compatibility problems in this cycle. Remaining on it also increasingly constrains PHP, framework-bundle, and third-party package upgrades, because maintained libraries commonly raise their supported Symfony and PHP baselines. An eventual upgrade becomes more expensive when deprecated 4.1-era APIs, legacy configuration, and untested dependency constraints accumulate across several intervening Symfony versions.

Treat the move as a supported-target migration rather than a permanent 4.1 maintenance task. Inventory the installed Symfony components, Symfony bundles, PHP version, application configuration, and locked transitive dependencies; then select a currently supported Symfony target compatible with the application and its required packages. Review the upgrade notes and deprecation notices for every version crossed, update dependencies in controlled stages where necessary, and resolve deprecations before attempting major-version changes. Run the full automated test suite, exercise authentication, messaging workers, cache invalidation, forms, commands, and production deployment paths, and keep a rollback plan for configuration or dependency regressions.