New in Symfony 4.1: Serialize and deserialize from abstract classes

Symfony 4.1 defines a new discriminator class mapping for the Serializer component so you can serialize and deserialize from abstract classes and interfaces.

New in Symfony 4.1: Prefix imported route names

Symfony 4.1 includes a new option called "name_prefix" to define the prefix added to all the routes imported in a configuration file.

New in Symfony 4.1: HTML5 Email Validation

Symfony 4.1 adds a new email address validation mode that uses the validation logic defined in the HTML5 specification.

New in Symfony 3.4: session improvements

Symfony 3.4 implements PHP's SessionUpdateTimestampHandlerInterface to prevent session fixation issues and provide lazy-write in session handlers.

New in Symfony 3.4: debug:autowiring command

Symfony 3.4 includes a new debug:autowiring command so you can quickly know which type-hints must be used to inject the services.

New in Symfony 3.4: Disable global form themes

In Symfony 3.4 you can disable global form themes for specific forms thanks to the new "only" keyword added to the "form_theme" Twig tag.

New in Symfony 3.4: Guard authentication improvements

In Symfony 3.4, Guard authenticators can implement a new method called supports() to better separate the responsibilities of the getCredentials() method.

New in Symfony 3.4: debug:form command

Symfony 3.4 adds a new command called debug:form to introspect all the information available for form types and their options.

New in Symfony 3.4: Local service binding

Symfony 3.4 allows binding services and parameters in local configuration files to avoid duplicating them in multiple service definitions.

New in Symfony 3.4: Services are private by default

In Symfony 3.4 services and aliases are private by default. This may require you to change some service definitions in your bundles and applications.