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Advanced Container Configuration

2.2 version
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Advanced Container Configuration

Marking Services as public / private

When defining services, you'll usually want to be able to access these definitions within your application code. These services are called public. For example, the doctrine service registered with the container when using the DoctrineBundle is a public service as you can access it via:

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$doctrine = $container->get('doctrine');

However, there are use-cases when you don't want a service to be public. This is common when a service is only defined because it could be used as an argument for another service.

Note

If you use a private service as an argument to only one other service, this will result in an inlined instantiation (e.g. new PrivateFooBar()) inside this other service, making it publicly unavailable at runtime.

Simply said: A service will be private when you do not want to access it directly from your code.

Here is an example:

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    services:
       foo:
         class: Example\Foo
         public: false
    
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    <service id="foo" class="Example\Foo" public="false" />
    
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    $definition = new Definition('Example\Foo');
    $definition->setPublic(false);
    $container->setDefinition('foo', $definition);
    

Now that the service is private, you cannot call:

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$container->get('foo');

However, if a service has been marked as private, you can still alias it (see below) to access this service (via the alias).

Note

Services are by default public.

Synthetic Services

Synthetic services are services that are injected into the container instead of being created by the container.

For example, if you're using the HttpKernel component with the DependencyInjection component, then the request service is injected in the ContainerAwareHttpKernel::handle() method when entering the request scope. The class does not exist when there is no request, so it can't be included in the container configuration. Also, the service should be different for every subrequest in the application.

To create a synthetic service, set synthetic to true:

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    services:
        request:
            synthetic: true
    
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    <service id="request"
        synthetic="true" />
    
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    use Symfony\Component\DependencyInjection\Definition;
    
    // ...
    $container->setDefinition('request', new Definition())
        ->setSynthetic(true);
    

As you see, only the synthetic option is set. All other options are only used to configure how a service is created by the container. As the service isn't created by the container, these options are omitted.

Now, you can inject the class by using Container::set:

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// ...
$container->set('request', new MyRequest(...));

Aliasing

You may sometimes want to use shortcuts to access some services. You can do so by aliasing them and, furthermore, you can even alias non-public services.

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    services:
       foo:
         class: Example\Foo
       bar:
         alias: foo
    
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    <service id="foo" class="Example\Foo"/>
    
    <service id="bar" alias="foo" />
    
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    $definition = new Definition('Example\Foo');
    $container->setDefinition('foo', $definition);
    
    $containerBuilder->setAlias('bar', 'foo');
    

This means that when using the container directly, you can access the foo service by asking for the bar service like this:

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$container->get('bar'); // Would return the foo service

Requiring files

There might be use cases when you need to include another file just before the service itself gets loaded. To do so, you can use the file directive.

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    services:
       foo:
         class: Example\Foo\Bar
         file: "%kernel.root_dir%/src/path/to/file/foo.php"
    
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    <service id="foo" class="Example\Foo\Bar">
        <file>%kernel.root_dir%/src/path/to/file/foo.php</file>
    </service>
    
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    $definition = new Definition('Example\Foo\Bar');
    $definition->setFile('%kernel.root_dir%/src/path/to/file/foo.php');
    $container->setDefinition('foo', $definition);
    

Notice that Symfony will internally call the PHP function require_once which means that your file will be included only once per request.

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