Environment Variables

Symfony will grab any environment variable prefixed with SYMFONY__ and set it as a parameter in the service container. Some transformations are applied to the resulting parameter name:

• SYMFONY__ prefix is removed;
• Parameter name is lowercased;
• 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 SetEnv directive with the following VirtualHost configuration:

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<VirtualHost *:80>
    ServerName      Symfony
    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>

For Nginx web servers, the environment variables can be set with the fastcgi_param directive. For example, in the configuration file where the fastcgi_params file is included:

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server {
    server_name domain.tld www.domain.tld;
    root /var/www/project/web;

    location / {
        try_files $uri /app.php$is_args$args;
    }

    location ~ ^/app\.php(/|$) {
        fastcgi_pass unix:/var/run/php5-fpm.sock;
        fastcgi_split_path_info ^(.+\.php)(/.*)$;
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $realpath_root$fastcgi_script_name;
        fastcgi_param DOCUMENT_ROOT $realpath_root;
        fastcgi_param SYMFONY__DATABASE__USER user;
        fastcgi_param SYMFONY__DATABASE__PASSWORD secret;
        internal;
    }

    # ...
}

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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:   symfony_project
        user:     '%database.user%'
        password: '%database.password%'

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

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

</container>

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$container->loadFromExtension('doctrine', array(
    'dbal' => array(
        'driver'   => 'pdo_mysql',
        'dbname'   => 'symfony_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 -->
<?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">

    <imports>
        <import resource="parameters.php" />
    </imports>

</container>

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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);