How to Set external Parameters in the Service Container

At times, it may benefit your application to store certain credentials outside of your project code. Database configuration is one such example. The flexibility of the Symfony service container allows you to easily do this.

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 followingVirtualHost configuration:

<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>

The example above is for an Apache configuration, using the SetEnv directive. However, this will work for any web server which supports the setting of environment variables.

Also, in order for your console to work (which does not use Apache), you must export these as shell variables. On a Unix system, you can run the following:

$ 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.

$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 Constants as 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.

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

A resource file can be one of many types. PHP, XML, YAML, INI, and closure resources are all supported by the imports directive.

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.

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

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