Environment Variables

Symfony will grab any environment variable prefixed with SYMFONY__ and set it as a parameter in the service container. Double underscores are replaced with a period, as a period is not a valid character in an environment variable name.

For example, if you're using Apache, environment variables can be set using the following VirtualHost configuration:

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<VirtualHost *:80>
    ServerName      Symfony2
    DocumentRoot    "/path/to/symfony_2_app/web"
    DirectoryIndex  index.php index.html
    SetEnv          SYMFONY__DATABASE__USER user
    SetEnv          SYMFONY__DATABASE__PASSWORD secret

    <Directory "/path/to/symfony_2_app/web">
        AllowOverride All
        Allow from All
    </Directory>
</VirtualHost>

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$ export SYMFONY__DATABASE__USER=user
$ export SYMFONY__DATABASE__PASSWORD=secret

Now that you have declared an environment variable, it will be present in the PHP $_SERVER global variable. Symfony then automatically sets all $_SERVER variables prefixed with SYMFONY__ as parameters in the service container.

You can now reference these parameters wherever you need them.

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doctrine:
    dbal:
        driver    pdo_mysql
        dbname:   symfony2_project
        user:     "%database.user%"
        password: "%database.password%"

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<!-- xmlns:doctrine="http://symfony.com/schema/dic/doctrine" -->
<!-- xsi:schemaLocation="http://symfony.com/schema/dic/doctrine http://symfony.com/schema/dic/doctrine/doctrine-1.0.xsd"> -->

<doctrine:config>
    <doctrine:dbal
        driver="pdo_mysql"
        dbname="symfony2_project"
        user="%database.user%"
        password="%database.password%"
    />
</doctrine:config>

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$container->loadFromExtension('doctrine', array(
    'dbal' => array(
        'driver'   => 'pdo_mysql',
        'dbname'   => 'symfony2_project',
        'user'     => '%database.user%',
        'password' => '%database.password%',
    )
));

Constants

The container also has support for setting PHP constants as parameters. See Introduction to Parameters for more details.

Miscellaneous Configuration

The imports directive can be used to pull in parameters stored elsewhere. Importing a PHP file gives you the flexibility to add whatever is needed in the container. The following imports a file named parameters.php.

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# app/config/config.yml
imports:
    - { resource: parameters.php }

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<!-- app/config/config.xml -->
<imports>
    <import resource="parameters.php" />
</imports>

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// app/config/config.php
$loader->import('parameters.php');

In parameters.php, tell the service container the parameters that you wish to set. This is useful when important configuration is in a non-standard format. The example below includes a Drupal database configuration in the Symfony service container.

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// app/config/parameters.php
include_once('/path/to/drupal/sites/default/settings.php');
$container->setParameter('drupal.database.url', $db_url);