Autowiring

Autowiring is an exotic word that represents something very simple: the ability of the container to automatically create and inject dependencies.

In order to achieve that, PHP-DI uses PHP's reflection to detect what parameters a constructor needs.

Autowiring does not affect performance when compiling the container.

Let's take this example:

class UserRepository
{
    // ...
}

class UserRegistrationService
{
    public function __construct(UserRepository $repository)
    {
        // ...
    }
}

When PHP-DI needs to create the UserRegistrationService, it detects that the constructor takes a UserRepository object (using the type declarations).

Without any configuration, PHP-DI will create a UserRepository instance (if it wasn't already created) and pass it as a constructor parameter. The equivalent raw PHP code would be:

$repository = new UserRepository();
$service = new UserRegistrationService($repository);

As you can imagine, it's very simple, doesn't require any configuration, and it just works!

Configuration

Autowiring is enabled by default. You can disable it using the container builder:

$containerBuilder->useAutowiring(false);

Limitations

PHP-DI won't be able to resolve cases like this:

class Database
{
    public function __construct($dbHost, $dbPort)
    {
        // ...
    }

    public function setLogger(LoggerInterface $logger)
    {
        // ...
    }
}

• it will not know what parameters to give to the constructor (since there is no type-hinting for an object)
• setLogger() will not be called

For those classes, you will need to use DI\autowire() in PHP definitions to declare explicitly what to inject.

PHP-DI is also unable to use Reflection on any PHP-internal classes like such that provide access to extension capabilities. Examples include Memcached, Gearman, any Curl* classes, anything from the SPL classes like RecursiveIteratorIterator, and so on. If you want to instantiate any class provided by the PHP engine or an extension, you have to provide explicit constructor parameters to PHP-DI.