.. index::
   single: Bundles

The Bundle System

A bundle is similar to a plugin in other software, but even better. The key difference is that everything is a bundle in Symfony, including both the core framework functionality and the code written for your application. Bundles are first-class citizens in Symfony. This gives you the flexibility to use pre-built features packaged in third-party bundles or to distribute your own bundles. It makes it easy to pick and choose which features to enable in your application and to optimize them the way you want.

Note

While you'll learn the basics here, an entire article is devoted to the organization and best practices of :doc:`bundles </bundles/best_practices>`.

A bundle is simply a structured set of files within a directory that implement a single feature. You might create a BlogBundle, a ForumBundle or a bundle for user management (many of these exist already as open source bundles). Each directory contains everything related to that feature, including PHP files, templates, stylesheets, JavaScript files, tests and anything else. Every aspect of a feature exists in a bundle and every feature lives in a bundle.

Bundles used in your applications must be enabled by registering them in the registerBundles() method of the AppKernel class:

// app/AppKernel.php
public function registerBundles()
{
    $bundles = array(
        new Symfony\Bundle\FrameworkBundle\FrameworkBundle(),
        new Symfony\Bundle\SecurityBundle\SecurityBundle(),
        new Symfony\Bundle\TwigBundle\TwigBundle(),
        new Symfony\Bundle\MonologBundle\MonologBundle(),
        new Symfony\Bundle\SwiftmailerBundle\SwiftmailerBundle(),
        new Symfony\Bundle\DoctrineBundle\DoctrineBundle(),
        new Symfony\Bundle\AsseticBundle\AsseticBundle(),
        new Sensio\Bundle\FrameworkExtraBundle\SensioFrameworkExtraBundle(),
        new AppBundle\AppBundle(),
    );

    if (in_array($this->getEnvironment(), array('dev', 'test'))) {
        $bundles[] = new Symfony\Bundle\WebProfilerBundle\WebProfilerBundle();
        $bundles[] = new Sensio\Bundle\DistributionBundle\SensioDistributionBundle();
        $bundles[] = new Sensio\Bundle\GeneratorBundle\SensioGeneratorBundle();
    }

    return $bundles;
}

With the registerBundles() method, you have total control over which bundles are used by your application (including the core Symfony bundles).

Tip

A bundle can live anywhere as long as it can be autoloaded (via the autoloader configured at app/autoload.php).

Creating a Bundle

SensioGeneratorBundle is an optional bundle that includes commands to create different elements of your application, such as bundles. If you create lots of bundles, consider using it. However, this section creates and enables a new bundle by hand to show how simple it is to do it.

The new bundle is called AcmeTestBundle, where the Acme portion is just a dummy 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 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 via the AppKernel class:

// app/AppKernel.php
public function registerBundles()
{
    $bundles = array(
        // ...
        // register your bundle
        new Acme\TestBundle\AcmeTestBundle(),
    );
    // ...

    return $bundles;
}

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

And as easy as this is, Symfony also provides a command-line interface for generating a basic bundle skeleton:

$ php app/console generate:bundle --namespace=Acme/TestBundle

The bundle skeleton generates a basic controller, template and routing resource that can be customized. You'll learn more about Symfony's command-line tools later.

Tip

Whenever creating a new bundle or using a third-party bundle, always make sure the bundle has been enabled in registerBundles(). When using the generate:bundle command, this is done for you.

Bundle Directory Structure

The directory structure of a bundle is simple and flexible. By default, the bundle system follows a set of conventions that help to keep code consistent between all Symfony bundles. Take a look at AcmeDemoBundle, as it contains some of the most common elements of a bundle:

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.yml).
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 web/ 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.

Learn more

.. toctree::
    :maxdepth: 1
    :glob:

    bundles/*

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