WARNING: You are browsing the documentation for Symfony 4.2 which is not maintained anymore. Consider upgrading your projects to Symfony 4.3.

You are browsing the Symfony 4.2 documentation, which changes significantly from Symfony 3.x. If your app doesn't use Symfony 4.2 yet, browse the Symfony 3.4 documentation.

Environment Variable Processors

4.2 version

Environment Variable Processors

Using env vars to configure Symfony applications is a common practice to hide sensitive configuration (e.g. database credentials) and to make your applications truly dynamic.

The main issue of env vars is that their values can only be strings and your application may need other data types (integer, boolean, etc.). Symfony solves this problem with "env var processors", which transform the original contents of the given environment variables. The following example uses the integer processor to turn the value of the HTTP_PORT env var into an integer:

  • YAML
    1
    2
    3
    4
    # config/packages/framework.yaml
    framework:
        router:
            http_port: '%env(int:HTTP_PORT)%'
    
  • XML
     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    14
    <!-- config/packages/framework.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">
    
        <framework:config>
            <framework:router http-port="%env(int:HTTP_PORT)%"/>
        </framework:config>
    </container>
    
  • PHP
    1
    2
    3
    4
    5
    6
    // config/packages/framework.php
    $container->loadFromExtension('framework', [
        'router' => [
            'http_port' => '%env(int:HTTP_PORT)%',
        ],
    ]);
    

Built-In Environment Variable Processors

Symfony provides the following env var processors:

env(string:FOO)

Casts FOO to a string:

  • YAML
    1
    2
    3
    4
    5
    # config/packages/framework.yaml
    parameters:
        env(SECRET): 'some_secret'
    framework:
        secret: '%env(string:SECRET)%'
    
  • XML
     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    14
    15
    16
    <!-- config/packages/framework.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="env(SECRET)">some_secret</parameter>
        </parameters>
    
        <framework:config secret="%env(string:SECRET)%"/>
    </container>
    
  • PHP
    1
    2
    3
    4
    5
    // config/packages/framework.php
    $container->setParameter('env(SECRET)', 'some_secret');
    $container->loadFromExtension('framework', [
        'secret' => '%env(string:SECRET)%',
    ]);
    
env(bool:FOO)

Casts FOO to a bool:

  • YAML
    1
    2
    3
    4
    5
    # config/packages/framework.yaml
    parameters:
        env(HTTP_METHOD_OVERRIDE): 'true'
    framework:
        http_method_override: '%env(bool:HTTP_METHOD_OVERRIDE)%'
    
  • XML
     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    14
    15
    16
    <!-- config/packages/framework.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="env(HTTP_METHOD_OVERRIDE)">true</parameter>
        </parameters>
    
        <framework:config http-methode-override="%env(bool:HTTP_METHOD_OVERRIDE)%"/>
    </container>
    
  • PHP
    1
    2
    3
    4
    5
    // config/packages/framework.php
    $container->setParameter('env(HTTP_METHOD_OVERRIDE)', 'true');
    $container->loadFromExtension('framework', [
        'http_method_override' => '%env(bool:HTTP_METHOD_OVERRIDE)%',
    ]);
    
env(int:FOO)
Casts FOO to an int.
env(float:FOO)
Casts FOO to a float.
env(const:FOO)

Finds the const value named in FOO:

  • YAML
    1
    2
    3
    4
    5
    6
    # config/packages/security.yaml
    parameters:
        env(HEALTH_CHECK_METHOD): 'Symfony\Component\HttpFoundation\Request::METHOD_HEAD'
    security:
        access_control:
            - { path: '^/health-check$', methods: '%env(const:HEALTH_CHECK_METHOD)%' }
    
  • XML
     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    14
    15
    16
    <!-- config/packages/security.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:security="http://symfony.com/schema/dic/security"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd">
    
        <parameters>
            <parameter key="env(HEALTH_CHECK_METHOD)">Symfony\Component\HttpFoundation\Request::METHOD_HEAD</parameter>
        </parameters>
    
        <security:config>
            <rule path="^/health-check$" methods="%env(const:HEALTH_CHECK_METHOD)%"/>
        </security:config>
    </container>
    
  • PHP
     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    // config/packages/security.php
    $container->setParameter('env(HEALTH_CHECK_METHOD)', 'Symfony\Component\HttpFoundation\Request::METHOD_HEAD');
    $container->loadFromExtension('security', [
        'access_control' => [
            [
                'path' => '^/health-check$',
                'methods' => '%env(const:HEALTH_CHECK_METHOD)%',
            ],
        ],
    ]);
    
env(base64:FOO)
Decodes the content of FOO, which is a base64 encoded string.
env(json:FOO)

Decodes the content of FOO, which is a JSON encoded string. It returns either an array or null:

  • YAML
    1
    2
    3
    4
    5
    # config/packages/framework.yaml
    parameters:
        env(TRUSTED_HOSTS): '["10.0.0.1", "10.0.0.2"]'
    framework:
        trusted_hosts: '%env(json:TRUSTED_HOSTS)%'
    
  • XML
     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    14
    15
    16
    <!-- config/packages/framework.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="env(TRUSTED_HOSTS)">["10.0.0.1", "10.0.0.2"]</parameter>
        </parameters>
    
        <framework:config trusted-hosts="%env(json:TRUSTED_HOSTS)%"/>
    </container>
    
  • PHP
    1
    2
    3
    4
    5
    // config/packages/framework.php
    $container->setParameter('env(TRUSTED_HOSTS)', '["10.0.0.1", "10.0.0.2"]');
    $container->loadFromExtension('framework', [
        'trusted_hosts' => '%env(json:TRUSTED_HOSTS)%',
    ]);
    
env(resolve:FOO)

Replaces the string FOO by the value of a config parameter with the same name:

  • YAML
    1
    2
    3
    4
    5
    6
    7
    # config/packages/sentry.yaml
    parameters:
        env(HOST): '10.0.0.1'
        sentry_host: '%env(HOST)%'
        env(SENTRY_DSN): 'http://%sentry_host%/project'
    sentry:
        dsn: '%env(resolve:SENTRY_DSN)%'
    
  • XML
     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    14
    15
    <!-- config/packages/sentry.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
            https://symfony.com/schema/dic/services/services-1.0.xsd">
    
        <parameters>
            <parameter key="env(HOST)">10.0.0.1</parameter>
            <parameter key="sentry_host">%env(HOST)%</parameter>
            <parameter key="env(SENTRY_DSN)">http://%sentry_host%/project</parameter>
        </parameters>
    
        <sentry:config dsn="%env(resolve:SENTRY_DSN)%"/>
    </container>
    
  • PHP
    1
    2
    3
    4
    5
    6
    7
    // config/packages/sentry.php
    $container->setParameter('env(HOST)', '10.0.0.1');
    $container->setParameter('sentry_host', '%env(HOST)%');
    $container->setParameter('env(SENTRY_DSN)', 'http://%sentry_host%/project');
    $container->loadFromExtension('sentry', [
        'dsn' => '%env(resolve:SENTRY_DSN)%',
    ]);
    
env(csv:FOO)

Decodes the content of FOO, which is a CSV-encoded string:

1
2
3
4
parameters:
    env(TRUSTED_HOSTS): "10.0.0.1, 10.0.0.2"
framework:
   trusted_hosts: '%env(csv:TRUSTED_HOSTS)%'
env(file:FOO)

Returns the contents of a file whose path is the value of the FOO env var:

  • YAML
    1
    2
    3
    4
    5
    # config/packages/framework.yaml
    parameters:
        env(AUTH_FILE): '../config/auth.json'
    google:
        auth: '%env(file:AUTH_FILE)%'
    
  • XML
     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    14
    15
    16
    <!-- config/packages/framework.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="env(AUTH_FILE)">../config/auth.json</parameter>
        </parameters>
    
        <google auth="%env(file:AUTH_FILE)%"/>
    </container>
    
  • PHP
    1
    2
    3
    4
    5
    // config/packages/framework.php
    $container->setParameter('env(AUTH_FILE)', '../config/auth.json');
    $container->loadFromExtension('google', [
        'auth' => '%env(file:AUTH_FILE)%',
    ]);
    
env(key:FOO:BAR)

Retrieves the value associated with the key FOO from the array whose contents are stored in the BAR env var:

  • YAML
    1
    2
    3
    4
    5
    # config/services.yaml
    parameters:
        env(SECRETS_FILE): '/opt/application/.secrets.json'
        database_password: '%env(key:database_password:json:file:SECRETS_FILE)%'
        # if SECRETS_FILE contents are: {"database_password": "secret"} it returns "secret"
    
  • XML
     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    14
    15
    <!-- 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="env(SECRETS_FILE)">/opt/application/.secrets.json</parameter>
            <parameter key="database_password">%env(key:database_password:json:file:SECRETS_FILE)%</parameter>
        </parameters>
    </container>
    
  • PHP
    1
    2
    3
    // config/services.php
    $container->setParameter('env(SECRETS_FILE)', '/opt/application/.secrets.json');
    $container->setParameter('database_password', '%env(key:database_password:json:file:SECRETS_FILE)%');
    

It is also possible to combine any number of processors:

1
2
3
4
5
6
7
8
parameters:
    env(AUTH_FILE): "%kernel.project_dir%/config/auth.json"
google:
    # 1. gets the value of the AUTH_FILE env var
    # 2. replaces the values of any config param to get the config path
    # 3. gets the content of the file stored in that path
    # 4. JSON-decodes the content of the file and returns it
    auth: '%env(json:file:resolve:AUTH_FILE)%'

Custom Environment Variable Processors

It's also possible to add your own processors for environment variables. First, create a class that implements EnvVarProcessorInterface:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
use Symfony\Component\DependencyInjection\EnvVarProcessorInterface;

class LowercasingEnvVarProcessor implements EnvVarProcessorInterface
{
    public function getEnv($prefix, $name, \Closure $getEnv)
    {
        $env = $getEnv($name);

        return strtolower($env);
    }

    public static function getProvidedTypes()
    {
        return [
            'lowercase' => 'string',
        ];
    }
}

To enable the new processor in the app, register it as a service and tag it with the container.env_var_processor tag. If you're using the default services.yaml configuration, this is already done for you, thanks to autoconfiguration.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.