You must upgrade your applications to the [latest supported runtime version](https://docs.cloud.google.com/appengine/docs/standard/lifecycle/support-schedule#php) to continue receiving security updates and be eligible for technical support. The process of upgrading an existing app depends on the runtime version that your app currently uses: - **PHP 5.5 (first-generation runtime)** : You must migrate your app to the [latest supported PHP version](https://docs.cloud.google.com/appengine/docs/standard/lifecycle/support-schedule#php). PHP 5.5 has reached [end of support](https://docs.cloud.google.com/appengine/docs/standard/lifecycle/runtime-lifecycle#end_of_support) on January 30, 2024. Your existing PHP 5.5 applications will continue to run and receive traffic. However, App Engine might block re-deployment of applications that use runtimes [after their end of support date](https://docs.cloud.google.com/appengine/docs/standard/lifecycle/support-schedule#php). To migrate to the latest supported version of PHP, see [Migrate from PHP 5.5 to the latest PHP runtime](https://docs.cloud.google.com/appengine/migration-center/standard/migrate-to-second-gen/php-differences). - **PHP second-generation runtimes (after end of support)** : To upgrade to a [supported version of PHP](https://docs.cloud.google.com/appengine/docs/standard/lifecycle/support-schedule#php), update the `app.yaml` file by specifying a version of PHP that you want your app to run. For example: runtime: phpVERSION Where VERSION is the PHP `MAJOR` and `MINOR` version numbers. For example, to use the latest PHP version, PHP 8.5, specify `85`. For more information, see the [PHP runtime overview](https://docs.cloud.google.com/appengine/docs/standard/php-gen2/runtime).