New in Symfony 3.4: Advanced environment variables

Symfony 3.4 allows to define the data type of the value stored in environment variables and also defines some operators to transform their values before using them.

New in Symfony 3.4: Improved comparison constraints

In Symfony 3.4, comparison constraints can get the value of any other property without having to define a full expression.

New in Symfony 3.4: Subscribing to events in the micro kernel

In Symfony 3.4, the MicroKernel trait can subscribe to events and handle them using methods defined in the kernel class.

New in Symfony 3.4: Deprecate configuration options

In Symfony 3.4, configuration options can be deprecated more easily to warn users about future changes.

New in Symfony 3.4: HTTP Immutable Responses

Symfony 3.4 will include support for HTTP Immutable Responses thanks to the new immutable option of the Cache-Control directive.

New in Symfony 3.4: Groups support for the Valid constraint

Symfony 3.4 adds support for validation groups in the Valid constraint, so you can partially validate the embedded objects.

New in Symfony 3.4: Better console exceptions

Symfony 3.4 improves the exceptions displayed in the console to include by default the exact file and line number where the exception occurred.

New in Symfony 3.4: User impersonation improvements

Symfony 3.4 improves the user impersonation feature of the Symfony component to make it easier to debug.

New in Symfony 3.4: Improved security listeners

In Symfony 3.4, security listeners are lazy loaded to improve performance. In addition, the Symfony Profiler has been updated to show all the information about security listeners.

New in Symfony 3.4: Added support for XLIFF 2.0 notes

Symfony 3.4 adds support for XLIFF 2.0 notes, which allow to store end user comments and annotations about translations.