Getting and Setting Container Parameters

Working with container parameters is straightforward using the container's accessor methods for parameters. You can check if a parameter has been defined in the container with:

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$container->hasParameter('mailer.transport');

You can retrieve a parameter set in the container with:

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$container->getParameter('mailer.transport');

and set a parameter in the container with:

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$container->setParameter('mailer.transport', 'sendmail');

Parameters in Configuration Files

You can also use the parameters section of a config file to set parameters:

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parameters:
    mailer.transport: sendmail

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<parameters>
    <parameter key="mailer.transport">sendmail</parameter>
</parameters>

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$container->setParameter('mailer.transport', 'sendmail');

As well as retrieving the parameter values directly from the container you can use them in the config files. You can refer to parameters elsewhere by surrounding them with percent (%) signs, e.g. %mailer.transport%. One use for this is to inject the values into your services. This allows you to configure different versions of services between applications or multiple services based on the same class but configured differently within a single application. You could inject the choice of mail transport into the Mailer class directly. But declaring it as a parameter makes it easier to change rather than being tied up and hidden with the service definition:

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parameters:
    mailer.transport: sendmail

services:
    mailer:
        class:     Mailer
        arguments: ['%mailer.transport%']

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<parameters>
    <parameter key="mailer.transport">sendmail</parameter>
</parameters>

<services>
    <service id="mailer" class="Mailer">
        <argument>%mailer.transport%</argument>
    </service>
</services>

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use Symfony\Component\DependencyInjection\Reference;

// ...
$container->setParameter('mailer.transport', 'sendmail');
$container
    ->register('mailer', 'Mailer')
    ->addArgument('%mailer.transport%');

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<parameter key="mailer.transport">
    sendmail
</parameter>

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<parameter key="mailer.transport">sendmail</parameter>

If you were using this elsewhere as well, then you would only need to change the parameter value in one place if needed.

You can also use the parameters in the service definition, for example, making the class of a service a parameter:

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parameters:
    mailer.transport: sendmail
    mailer.class: Mailer

services:
    mailer:
        class:     '%mailer.class%'
        arguments: ['%mailer.transport%']

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<parameters>
    <parameter key="mailer.transport">sendmail</parameter>
    <parameter key="mailer.class">Mailer</parameter>
</parameters>

<services>
    <service id="mailer" class="%mailer.class%">
        <argument>%mailer.transport%</argument>
    </service>

</services>

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use Symfony\Component\DependencyInjection\Reference;

// ...
$container->setParameter('mailer.transport', 'sendmail');
$container->setParameter('mailer.class', 'Mailer');
$container
    ->register('mailer', '%mailer.class%')
    ->addArgument('%mailer.transport%');

$container
    ->register('newsletter_manager', 'NewsletterManager')
    ->addMethodCall('setMailer', array(new Reference('mailer')));

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arguments: ['http://symfony.com/?foo=%%s&bar=%%d']

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<argument type="string">http://symfony.com/?foo=%%s&bar=%%d</argument>

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->addArgument('http://symfony.com/?foo=%%s&bar=%%d');

Array Parameters

Parameters do not need to be flat strings, they can also be arrays. For the XML format, you need to use the type="collection" attribute for all parameters that are arrays.

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# app/config/config.yml
parameters:
    my_mailer.gateways:
        - mail1
        - mail2
        - mail3
    my_multilang.language_fallback:
        en:
            - en
            - fr
        fr:
            - fr
            - en

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<!-- app/config/config.xml -->
<parameters>
    <parameter key="my_mailer.gateways" type="collection">
        <parameter>mail1</parameter>
        <parameter>mail2</parameter>
        <parameter>mail3</parameter>
    </parameter>
    <parameter key="my_multilang.language_fallback" type="collection">
        <parameter key="en" type="collection">
            <parameter>en</parameter>
            <parameter>fr</parameter>
        </parameter>
        <parameter key="fr" type="collection">
            <parameter>fr</parameter>
            <parameter>en</parameter>
        </parameter>
    </parameter>
</parameters>

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// app/config/config.php
use Symfony\Component\DependencyInjection\Definition;

$container->setParameter('my_mailer.gateways', array('mail1', 'mail2', 'mail3'));
$container->setParameter('my_multilang.language_fallback', array(
    'en' => array('en', 'fr'),
    'fr' => array('fr', 'en'),
));

Constants as Parameters

The container also has support for setting PHP constants as parameters. To take advantage of this feature, map the name of your constant to a parameter key, and define the type as constant.

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<?xml version="1.0" encoding="UTF-8"?>

<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

    <parameters>
        <parameter key="global.constant.value" type="constant">GLOBAL_CONSTANT</parameter>
        <parameter key="my_class.constant.value" type="constant">My_Class::CONSTANT_NAME</parameter>
    </parameters>
</container>

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$container->setParameter('global.constant.value', GLOBAL_CONSTANT);
$container->setParameter('my_class.constant.value', My_Class::CONSTANT_NAME);

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

PHP Keywords in XML

By default, true, false and null in XML are converted to the PHP keywords (respectively true, false and null):

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<parameters>
    <parameter key="mailer.send_all_in_once">false</parameters>
</parameters>

<!-- after parsing
$container->getParameter('mailer.send_all_in_once'); // returns false
-->

To disable this behavior, use the string type:

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<parameters>
    <parameter key="mailer.some_parameter" type="string">true</parameter>
</parameters>

<!-- after parsing
$container->getParameter('mailer.some_parameter'); // returns "true"
-->

Syntax for Referencing Services

You can of course also reference services, which looks a bit different in each format. You can configure the behavior if the referenced service does not exist. By default, an exception is thrown when a non-existent service is referenced.