Best Practices for Reusable Bundles

Bundle Name

A bundle is also a PHP namespace. The namespace must follow the PSR-0 or PSR-4 interoperability standards for PHP namespaces and class names: it starts with a vendor segment, followed by zero or more category segments, and it ends with the namespace short name, which must end with Bundle.

A namespace becomes a bundle as soon as you add a bundle class to it. The bundle class name must follow these simple rules:

• Use only alphanumeric characters and underscores;
• Use a StudlyCaps name (i.e. camelCase with the first letter uppercased);
• Use a descriptive and short name (no more than two words);
• Prefix the name with the concatenation of the vendor (and optionally the category namespaces);
• Suffix the name with Bundle.

Here are some valid bundle namespaces and class names:

By convention, the getName() method of the bundle class should return the class name.

Each bundle has an alias, which is the lower-cased short version of the bundle name using underscores (acme_blog for AcmeBlogBundle). This alias is used to enforce uniqueness within a project and for defining bundle's configuration options (see below for some usage examples).

Directory Structure

The basic directory structure of an AcmeBlogBundle must read as follows:

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<your-bundle>/
├─ AcmeBlogBundle.php
├─ Controller/
├─ README.md
├─ LICENSE
├─ Resources/
│   ├─ config/
│   ├─ doc/
│   │  └─ index.rst
│   ├─ translations/
│   ├─ views/
│   └─ public/
└─ Tests/

The following files are mandatory, because they ensure a structure convention that automated tools can rely on:

• AcmeBlogBundle.php: This is the class that transforms a plain directory into a Symfony bundle (change this to your bundle's name);
• README.md: This file contains the basic description of the bundle and it usually shows some basic examples and links to its full documentation (it can use any of the markup formats supported by GitHub, such as README.rst);
• LICENSE: The full contents of the license used by the code. Most third-party bundles are published under the MIT license, but you can choose any license;
• Resources/doc/index.rst: The root file for the Bundle documentation.

The depth of subdirectories should be kept to a minimum for the most used classes and files. Two levels is the maximum.

The bundle directory is read-only. If you need to write temporary files, store them under the cache/ or log/ directory of the host application. Tools can generate files in the bundle directory structure, but only if the generated files are going to be part of the repository.

The following classes and files have specific emplacements (some are mandatory and others are just conventions followed by most developers):

Classes

The bundle directory structure is used as the namespace hierarchy. For instance, a ContentController controller which is stored in Acme/BlogBundle/Controller/ContentController.php would have the fully qualified class name of Acme\BlogBundle\Controller\ContentController.

All classes and files must follow the Symfony coding standards.

Some classes should be seen as facades and should be as short as possible, like Commands, Helpers, Listeners and Controllers.

Classes that connect to the event dispatcher should be suffixed with Listener.

Exception classes should be stored in an Exception sub-namespace.

Vendors

A bundle must not embed third-party PHP libraries. It should rely on the standard Symfony autoloading instead.

A bundle should also not embed third-party libraries written in JavaScript, CSS or any other language.

Tests

A bundle should come with a test suite written with PHPUnit and stored under the Tests/ directory. Tests should follow the following principles:

• The test suite must be executable with a simple phpunit command run from a sample application;
• The functional tests should only be used to test the response output and some profiling information if you have some;
• The tests should cover at least 95% of the code base.

Documentation

All classes and functions must come with full PHPDoc.

Extensive documentation should also be provided in the Resources/doc/ directory. The index file (for example Resources/doc/index.rst or Resources/doc/index.md) is the only mandatory file and must be the entry point for the documentation. The reStructuredText (rST) is the format used to render the documentation on symfony.com.

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Installation
============

Step 1: Download the Bundle
---------------------------

Open a command console, enter your project directory and execute the
following command to download the latest stable version of this bundle:

```console
$ composer require <package-name> "~1"
```

This command requires you to have Composer installed globally, as explained
in the [installation chapter](https://getcomposer.org/doc/00-intro.md)
of the Composer documentation.

Step 2: Enable the Bundle
-------------------------

Then, enable the bundle by adding it to the list of registered bundles
in the `app/AppKernel.php` file of your project:

```php
<?php
// app/AppKernel.php

// ...
class AppKernel extends Kernel
{
    public function registerBundles()
    {
        $bundles = array(
            // ...
            new <vendor>\<bundle-name>\<bundle-long-name>(),
        );

        // ...
    }

    // ...
}
```

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Installation
============

Step 1: Download the Bundle
---------------------------

Open a command console, enter your project directory and execute the
following command to download the latest stable version of this bundle:

.. code-block:: terminal

    $ composer require <package-name> "~1"

This command requires you to have Composer installed globally, as explained
in the `installation chapter`_ of the Composer documentation.

Step 2: Enable the Bundle
-------------------------

Then, enable the bundle by adding it to the list of registered bundles
in the ``app/AppKernel.php`` file of your project:

.. code-block:: php

    <?php
    // app/AppKernel.php

    // ...
    class AppKernel extends Kernel
    {
        public function registerBundles()
        {
            $bundles = array(
                // ...

                new <vendor>\<bundle-name>\<bundle-long-name>(),
            );

            // ...
        }

        // ...
    }

.. _`installation chapter`: https://getcomposer.org/doc/00-intro.md

Routing

If the bundle provides routes, they must be prefixed with the bundle alias. For example, if your bundle is called AcmeBlogBundle, all its routes must be prefixed with acme_blog_.

Templates

If a bundle provides templates, they must use Twig. A bundle must not provide a main layout, except if it provides a full working application.

Translation Files

If a bundle provides message translations, they must be defined in the XLIFF format; the domain should be named after the bundle name (acme_blog).

A bundle must not override existing messages from another bundle.

Configuration

To provide more flexibility, a bundle can provide configurable settings by using the Symfony built-in mechanisms.

For simple configuration settings, rely on the default parameters entry of the Symfony configuration. Symfony parameters are simple key/value pairs; a value being any valid PHP value. Each parameter name should start with the bundle alias, though this is just a best-practice suggestion. The rest of the parameter name will use a period (.) to separate different parts (e.g. acme_blog.author.email).

The end user can provide values in any configuration file:

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# app/config/config.yml
parameters:
    acme_blog.author.email: 'fabien@example.com'

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<!-- app/config/config.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd">

    <parameters>
        <parameter key="acme_blog.author.email">fabien@example.com</parameter>
    </parameters>

</container>

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// app/config/config.php
$container->setParameter('acme_blog.author.email', 'fabien@example.com');

Retrieve the configuration parameters in your code from the container:

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$container->getParameter('acme_blog.author.email');

Even if this mechanism is simple enough, you should consider using the more advanced semantic bundle configuration.

Versioning

Bundles must be versioned following the Semantic Versioning Standard.

Services

If the bundle defines services, they must be prefixed with the bundle alias. For example, AcmeBlogBundle services must be prefixed with acme_blog.

In addition, services not meant to be used by the application directly, should be defined as private.

Composer Metadata

The composer.json file should include at least the following metadata:

name

Consists of the vendor and the short bundle name. If you are releasing the bundle on your own instead of on behalf of a company, use your personal name (e.g. johnsmith/blog-bundle). Exclude the vendor name from the bundle short name and separate each word with an hyphen. For example: AcmeBlogBundle is transformed into blog-bundle and AcmeSocialConnectBundle is transformed into social-connect-bundle.

description

A brief explanation of the purpose of the bundle.

type

Use the symfony-bundle value.

license

a string (or array of strings) with a valid license identifier, such as MIT.

autoload

This information is used by Symfony to load the classes of the bundle. The PSR-4 autoload standard is recommended for modern bundles, but PSR-0 standard is also supported.

In order to make it easier for developers to find your bundle, register it on Packagist, the official repository for Composer packages.

Custom Validation Constraints

Starting with Symfony 2.5, a new Validation API was introduced. In fact, there are 3 modes, which the user can configure in their project:

• 2.4: the original 2.4 and earlier validation API;
• 2.5: the new 2.5 and later validation API;
• 2.5-BC: the new 2.5 API with a backwards-compatible layer so that the 2.4 API still works. This is only available in PHP 5.3.9+.

As a bundle author, you'll want to support both API's, since some users may still be using the 2.4 API. Specifically, if your bundle adds a violation directly to the ExecutionContext (e.g. like in a custom validation constraint), you'll need to check for which API is being used. The following code, would work for all users:

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use Symfony\Component\Validator\ConstraintValidator;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\Context\ExecutionContextInterface;
// ...

class ContainsAlphanumericValidator extends ConstraintValidator
{
    public function validate($value, Constraint $constraint)
    {
        if ($this->context instanceof ExecutionContextInterface) {
            // the 2.5 API
            $this->context->buildViolation($constraint->message)
                ->setParameter('%string%', $value)
                ->addViolation()
            ;
        } else {
            // the 2.4 API
            $this->context->addViolation(
                $constraint->message,
                array('%string%' => $value)
            );
        }
    }
}

Resources

If the bundle references any resources (config files, translation files, etc.), don't use physical paths (e.g. __DIR__/config/services.xml) but logical paths (e.g. @AppBundle/Resources/config/services.xml).

The logical paths are required because of the bundle overriding mechanism that lets you override any resource/file of any bundle. See The HttpKernel Component for more details about transforming physical paths into logical paths.

Beware that templates use a simplified version of the logical path shown above. For example, an index.html.twig template located in the Resources/views/Default/ directory of the AppBundle, is referenced as @App/Default/index.html.twig.

Learn more

• How to Load Service Configuration inside a Bundle
• How to Create Friendly Configuration for a Bundle