.. index::
   single: Bundles

The Bundle System

Caution!

In Symfony versions prior to 4.0, it was recommended to organize your own application code using bundles. This is no longer recommended and bundles should only be used to share code and features between multiple applications.

A bundle is similar to a plugin in other software, but even better. The core features of Symfony framework are implemented with bundles (FrameworkBundle, SecurityBundle, DebugBundle, etc.) They are also used to add new features in your application via third-party bundles.

Bundles used in your applications must be enabled per :ref:`environment <configuration-environments>` in the config/bundles.php file:

// config/bundles.php
return [
    // 'all' means that the bundle is enabled for any Symfony environment
    Symfony\Bundle\FrameworkBundle\FrameworkBundle::class => ['all' => true],
    Symfony\Bundle\SecurityBundle\SecurityBundle::class => ['all' => true],
    Symfony\Bundle\TwigBundle\TwigBundle::class => ['all' => true],
    Symfony\Bundle\MonologBundle\MonologBundle::class => ['all' => true],
    Symfony\Bundle\SwiftmailerBundle\SwiftmailerBundle::class => ['all' => true],
    Doctrine\Bundle\DoctrineBundle\DoctrineBundle::class => ['all' => true],
    Sensio\Bundle\FrameworkExtraBundle\SensioFrameworkExtraBundle::class => ['all' => true],
    // this bundle is enabled only in 'dev' and 'test', so you can't use it in 'prod'
    Symfony\Bundle\WebProfilerBundle\WebProfilerBundle::class => ['dev' => true, 'test' => true],
];

Tip

In a default Symfony application that uses :ref:`Symfony Flex <symfony-flex>`, bundles are enabled/disabled automatically for you when installing/removing them, so you don't need to look at or edit this bundles.php file.

Creating a Bundle

This section creates and enables a new bundle to show there are only a few steps required. The new bundle is called AcmeTestBundle, where the Acme portion is an example name that should be replaced by some "vendor" name that represents you or your organization (e.g. ABCTestBundle for some company named ABC).

Start by creating a src/Acme/TestBundle/ directory and adding a new file called AcmeTestBundle.php:

// src/Acme/TestBundle/AcmeTestBundle.php
namespace App\Acme\TestBundle;

use Symfony\Component\HttpKernel\Bundle\Bundle;

class AcmeTestBundle extends Bundle
{
}

Tip

The name AcmeTestBundle follows the standard :ref:`Bundle naming conventions <bundles-naming-conventions>`. You could also choose to shorten the name of the bundle to simply TestBundle by naming this class TestBundle (and naming the file TestBundle.php).

This empty class is the only piece you need to create the new bundle. Though commonly empty, this class is powerful and can be used to customize the behavior of the bundle. Now that you've created the bundle, enable it:

// config/bundles.php
return [
    // ...
    App\Acme\TestBundle\AcmeTestBundle::class => ['all' => true],
];

And while it doesn't do anything yet, AcmeTestBundle is now ready to be used.

Bundle Directory Structure

The directory structure of a bundle is meant to help to keep code consistent between all Symfony bundles. It follows a set of conventions, but is flexible to be adjusted if needed:

Controller/: Contains the controllers of the bundle (e.g. RandomController.php).
DependencyInjection/: Holds certain Dependency Injection Extension classes, which may import service configuration, register compiler passes or more (this directory is not necessary).
Resources/config/: Houses configuration, including routing configuration (e.g. routing.yaml).
Resources/views/: Holds templates organized by controller name (e.g. Random/index.html.twig).
Resources/public/: Contains web assets (images, stylesheets, etc) and is copied or symbolically linked into the project public/ directory via the assets:install console command.
Tests/: Holds all tests for the bundle.

A bundle can be as small or large as the feature it implements. It contains only the files you need and nothing else.

As you move through the guides, you'll learn how to persist objects to a database, create and validate forms, create translations for your application, write tests and much more. Each of these has their own place and role within the bundle.