New in Symfony 4.1: Prepared commands
In Symfony 4.1, the commands passed to the process component can contain placeholders whose values are defined at runtime or obtained through environment variables.
New in Symfony 4.1: Argon2i configuration
In Symfony 4.1 you can configure the cost of hashing a password with the Argon2i algorithm thanks to three new options called memory_cost, time_cost and threads.
New in Symfony 4.1: Deprecated the bundle notation
In Symfony 4.1, the bundle notation has been deprecated in favor of regular PHP namespaces.
New in Symfony 4.1: 307 and 308 redirections
Symfony 4.1 adds support for making 307 and 308 redirections, which are similar to 301 and 302 redirections but they don't allow changing the request method.
New in Symfony 4.1: Validator improvements
In Symfony 4.1, the Url, Locale and Expression constraints have been improved with new config options.
New in Symfony 4.1: Fastest PHP Router
In Symfony 4.1 applications, matching a URL is 77 times faster than in previous Symfony versions, becoming the fastest router available in PHP.
New in Symfony: Reproducible builds
Symfony applications starting from 3.4 are now compatible with "reproducible builds", a set of practices to ensure the same compilation result when the source code doesn't change.
New in Symfony 4.1: Added support for immutable dates in forms
Symfony 4.1 added support for DateTimeImmutable objects in every form type related to date and time.
New in Symfony 4.1: Getting container parameters as a service
In Symfony 4.1 you can get all container parameters in a service injecting one of its constructor arguments with the ParameterBagInterface.