.. index::
   single: Configuration

Configuring Symfony (and Environments)

Symfony applications can install third-party packages (bundles, libraries, etc.) to bring in new features (:doc:`services </service_container>`) to your project. Each package can be customized via configuration files that live - by default - in the config/ directory.

Configuration: config/packages/

The configuration for each package can be found in config/packages/. For instance, the framework bundle is configured in config/packages/framework.yaml:

.. configuration-block::

    .. code-block:: yaml

        # config/packages/framework.yaml
        framework:
            secret: '%env(APP_SECRET)%'
            #default_locale: en
            #csrf_protection: true
            #http_method_override: true

            # Enables session support. Note that the session will ONLY be started if you read or write from it.
            # Remove or comment this section to explicitly disable session support.
            session:
                handler_id: ~

            #esi: true
            #fragments: true
            php_errors:
                log: true

    .. code-block:: xml

            <!-- config/packages/framework.xml -->
            <?xml version="1.0" encoding="UTF-8" ?>
            <container xmlns="http://symfony.com/schema/dic/services"
                xmlns:framework="http://symfony.com/schema/dic/framework"
                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                xsi:schemaLocation="http://symfony.com/schema/dic/services https://symfony.com/schema/dic/services/services-1.0.xsd
                    http://symfony.com/schema/dic/framework https://symfony.com/schema/dic/framework/framework-1.0.xsd"
            >
                <framework:config secret="%env(APP_SECRET)%">
                    <!--<framework:csrf-protection enabled="true"/>-->
                    <!--<framework:esi enabled="true"/>-->
                    <!--<framework:fragments enabled="true"/>-->

                    <!-- Enables session support. Note that the session will ONLY be started if you read or write from it.
                         Remove or comment this section to explicitly disable session support. -->
                    <framework:session/>

                    <framework:php-errors log="true"/>
                </framework:config>
            </container>

    .. code-block:: php

        // config/packages/framework.php
        $container->loadFromExtension('framework', [
            'secret' => '%env(APP_SECRET)%',
            //'default_locale' => 'en',
            //'csrf_protection' => true,
            //'http_method_override' => true,

            // Enables session support. Note that the session will ONLY be started if you read or write from it.
            // Remove or comment this section to explicitly disable session support.
            'session' => [
                'handler_id' => null,
            ],
            //'esi' => true,
            //'fragments' => true,
            'php_errors' => [
                'log' => true,
            ],
        ]);

The top-level key (here framework) references configuration for a specific bundle (:doc:`FrameworkBundle </reference/configuration/framework>` in this case).

Configuration Formats

Throughout the documentation, all configuration examples will be shown in three formats (YAML, XML and PHP). YAML is used by default, but you can choose whatever you like best. There is no performance difference:

:doc:`/components/yaml/yaml_format`: Simple, clean and readable;
XML: More powerful than YAML at times & supports IDE autocompletion;
PHP: Very powerful but less readable than standard configuration formats.

Configuration Reference & Dumping

There are two ways to know what keys you can configure:

Use the :doc:`Reference Section </reference/index>`;
Use the config:dump-reference command.

For example, if you want to configure something related to the framework bundle, you can see an example dump of all available configuration options by running:

$ php bin/console config:dump-reference framework

.. index::
   single: Environments; Introduction

The parameters Key: Parameters (Variables)

The configuration has some special top-level keys. One of them is called parameters: it's used to define variables that can be referenced in any other configuration file. For example, when you install the translation package, a locale parameter is added to config/services.yaml:

.. configuration-block::

    .. code-block:: yaml

        # config/services.yaml
        parameters:
            locale: en

        # ...

    .. code-block:: xml

        <!-- config/services.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"
            xmlns:framework="http://symfony.com/schema/dic/symfony"
            xsi:schemaLocation="http://symfony.com/schema/dic/services
                https://symfony.com/schema/dic/services/services-1.0.xsd
                http://symfony.com/schema/dic/symfony
                https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">

            <parameters>
                <parameter key="locale">en</parameter>
            </parameters>

            <!-- ... -->
        </container>

    .. code-block:: php

        // config/services.php
        $container->setParameter('locale', 'en');
        // ...

This parameter is then referenced in the framework config in config/packages/translation.yaml:

.. configuration-block::

    .. code-block:: yaml

        # config/packages/translation.yaml
        framework:
            # any string surrounded by two % is replaced by that parameter value
            default_locale: '%locale%'

            # ...

    .. code-block:: xml

        <!-- config/packages/translation.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"
            xmlns:framework="http://symfony.com/schema/dic/symfony"
            xsi:schemaLocation="http://symfony.com/schema/dic/services
                https://symfony.com/schema/dic/services/services-1.0.xsd
                http://symfony.com/schema/dic/symfony
                https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">

            <!-- any string surrounded by two % is replaced by that parameter value -->
            <framework:config default-locale="%locale%">
                <!-- ... -->
            </framework:config>
        </container>

    .. code-block:: php

        // config/packages/translation.php
        $container->loadFromExtension('framework', [
            // any string surrounded by two % is replaced by that parameter value
            'default_locale' => '%locale%',

            // ...
        ]);

You can define whatever parameter names you want under the parameters key of any configuration file. To reference a parameter, surround its name with two percent signs - e.g. %locale%.

.. seealso::

    You can also set parameters dynamically, like from environment variables.
    See :doc:`/configuration/environment_variables`.

For more information about parameters - including how to reference them from inside a controller - see :ref:`service-container-parameters`.

The .env File & Environment Variables

There is also a .env file which is loaded and its contents become environment variables. This is useful during development, or if setting environment variables is difficult for your deployment.

When you install packages, more environment variables are added to this file. But you can also add your own.

Environment variables can be referenced in any other configuration files by using a special syntax. For example, if you install the doctrine package, then you will have an environment variable called DATABASE_URL in your .env file. This is referenced inside config/packages/doctrine.yaml:

# config/packages/doctrine.yaml
doctrine:
    dbal:
        url: '%env(DATABASE_URL)%'

        # The `resolve:` prefix replaces container params by their values inside the env variable:
        # url: '%env(resolve:DATABASE_URL)%'

For more details about environment variables, see :ref:`config-env-vars`.

Caution!

Applications created before November 2018 had a slightly different system, involving a .env.dist file. For information about upgrading, see: :doc:`configuration/dot-env-changes`.

The .env file is special, because it defines the values that usually change on each server. For example, the database credentials on your local development machine might be different from your workmates. The .env file should contain sensible, non-secret default values for all of your environment variables and should be commited to your repository.

To override these variables with machine-specific or sensitive values, create a .env.local file. This file is not committed to the shared repository and is only stored on your machine. In fact, the .gitignore file that comes with Symfony prevents it from being committed.

You can also create a few other .env files that will be loaded:

.env.{environment}: e.g. .env.test will be loaded in the test environment and committed to your repository.
.env.{environment}.local: e.g. .env.prod.local will be loaded in the prod environment but will not be committed to your repository.

If you decide to set real environment variables on production, the .env files are still loaded, but your real environment variables will override those values.

Environments & the Other Config Files

You have just one app, but whether you realize it or not, you need it to behave differently at different times:

While developing, you want your app to log everything and expose nice debugging tools;
After deploying to production, you want that same app to be optimized for speed and only log errors.

How can you make one application behave in two different ways? With environments.

You've probably already been using the dev environment without even knowing it. After you deploy, you'll use the prod environment.

To learn more about how to execute and control each environment, see :doc:`/configuration/environments`.

Keep Going!

Congratulations! You've tackled the basics in Symfony. Next, learn about each part of Symfony individually by following the guides. Check out:

:doc:`/forms`
:doc:`/doctrine`
:doc:`/service_container`
:doc:`/security`
:doc:`/email`
:doc:`/logging`

And the many other topics.

Learn more

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