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The new Symfony 3.3 Service Configuration Changes Explained

tl;dr Symfony 3.3 comes with some big new service configuration features. We've explained them here: The Symfony 3.3 DI Container Changes Explained

In less than 2 weeks, Symfony 3.3 will be released. It comes with a lot of new stuff, but there is one feature that stands out: the new service configuration. I am very excited about these changes: they're designed to accelerate development, make Symfony easier to learn and encourage best-practices (e.g. injecting specific dependencies instead of using $container->get())... without sacrificing predictability and stability.

If you haven't seen it yet, the services.yml file for a new Symfony 3.3 project will look like this:

services:
    # default configuration for services in *this* file
    _defaults:
        # automatically injects dependencies in your services
        autowire: true
        # automatically registers your services as commands, event subscribers, etc.
        autoconfigure: true
        # this means you cannot fetch services directly from the container via $container->get()
        # if you need to do this, you can override this setting on individual services
        public: false

    # makes classes in src/AppBundle available to be used as services
    # this creates a service per class whose id is the fully-qualified class name
    AppBundle\:
        resource: '../../src/AppBundle/*'
        # you can exclude directories or files
        # but if a service is unused, it's removed anyway
        exclude: '../../src/AppBundle/{Entity,Repository}'

    # controllers are imported separately to make sure they're public
    # and have a tag that allows actions to type-hint services
    AppBundle\Controller\:
        resource: '../../src/AppBundle/Controller'
        public: true
        tags: ['controller.service_arguments']

There's a lot going on, including service auto-registration, autowiring and auto-tagging (autoconfigure).

Of course, these features are (and will always be) optional: you can upgrade your project to Symfony 3.3 without making any changes. But, I hope you'll give these new features a chance: I've already upgraded a large project and love them.

We've written an in-depth article explaining all of this further on the documentation: The Symfony 3.3 DI Container Changes Explained.

Try it, and let us know what you think!