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.

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).

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.