README

Semperton Container

A lightweight PSR-11 dependency injection container
with reflection based autowiring.

Installation

Just use Composer:

composer require semperton/container

Container requires PHP 8.2+

Interface

new Container(iterable $definitions = [])

The container ships with these public methods:

withAutowiring(bool $flag): Container // toggle autowiring (disabled by default)
withEntry(string $id, mixed $entry): Container // add a container entry
withDelegate(ContainerInterface $delegate): Container // register a delegate container
get(string $id): mixed // get entry (PSR-11)
has(string $id): bool // has entry (PSR-11)
create(string $id, array $params = []): mixed // create a class with optional constructor substitution args
entries(): array // list all container entries

Usage

Classes can be resolved automatically as long as they do not require any special configuration (autowiring). Autowiring is disabled by default and has to be enabled explicitly:

use Semperton\Container\Container;

class World
{
	public function __toString()
	{
		return 'World';
	}
}

class Hello
{
	protected $world;
	public function __construct(World $world)
	{
		$this->world = $world;
	}
	public function print()
	{
		echo "Hello {$this->world}";
	}
}

$container = (new Container())->withAutowiring(true);
$hello = $container->get(Hello::class);
$hello2 = $container->get(Hello::class);

$hello instanceof Hello::class // true
$hello === $hello2 // true
$hello->print(); // 'Hello World'

Without autowiring, only configured entries, factories and the container itself (Container::class, ContainerInterface::class) can be resolved.

Note that the container only creates (shared) instances once. It does not work as a factory. You should consider the Factory Pattern or use the create() method instead:

use Semperton\Container\Container;

class Mail
{
	public function __construct(Config $c, string $to)
	{
	}
}

class MailFactory
{
	public function createMail(string $to)
	{
		return new Mail(new Config(), $to);
	}
}

$mail1 = $container->get(MailFactory::class)->createMail('info@example.com');
$mail2 = $container->create(Mail::class, ['to' =>'info@example.com']);

The create() method will automatically resolve the Config dependency for Mail. It always builds a new instance, either with the registered factory or through autowiring. Existing entries and delegate entries are never returned by create().

Parameter resolving

Factory and constructor params are resolved in this order:

params passed to create() (by name)
class-typed params the container can resolve
declared default values

Note that a resolvable class type always wins over a default value: Logger $logger = new NullLogger() receives the container's Logger when one can be resolved. Builtin types (string, int, ...), union and intersection types are never guessed. Pass them to create() or use a factory, otherwise a ParameterResolveException is thrown. Variadic params only receive values passed explicitly as an array ($container->create(Foo::class, ['items' => [$a, $b]])), otherwise they stay empty.

If an entry is known but one of its dependencies is missing, get() and create() throw a DependencyException (not a NotFoundExceptionInterface), with the original exception as previous.

Configuration

You can configure the container with definitions. Closures are always treated as factories and should be used to bootstrap class instances. If you like to use callables as factories: Closure::fromCallable([$object, 'method']).

use Semperton\Container\Container;

$container = new Container([

	'mail' => 'local@host.local',
	'closure' => static function () { // closures must be wrapped in another closure
		return static function () {
			return 42;
		};
	},
	MailFactory::class => new MailFactory('local@host.local'), // avoid this, instead do
	MailFactory::class => static function (Container $c) { // lazy instantiation with a factory

		$sender = $c->get('mail');
		return new MailFactory($sender);
	},
	// class-typed factory params are resolved from the container (configured entries or autowiring)
	Service::class => static fn (Dependency $dep) => new Service($dep)
]);

$container->get('mail'); // 'local@host.local'
$container->get('closure')(); // 42
$container->get(MailFactory::class); // instance of MailFactory

The withEntry() method also treats Closures as factories.

Immutability

Once the container is created, it is immutable. If you like to add an entry after instantiation, keep in mind that the withEntry() method always returns a new container instance:

use Semperton\Container\Container;

$container1 = new Container();
$container2 = $container1->withEntry('number', 42);

$container1->has('number'); // false
$container2->has('number'); // true

$container1 === $container2 // false

A new container instance does not share already resolved instances with its origin, so replaced entries are always taken into account:

$container1 = new Container([
	Dependency::class => new Dependency(),
	Service::class => static fn (Dependency $dep) => new Service($dep)
]);

$service1 = $container1->get(Service::class);
$service2 = $container1->withEntry(Dependency::class, new Dependency())->get(Service::class);

$service1 === $service2 // false

Upgrading from 3.x

PHP 8.2+ is required.
Autowiring is disabled by default. Call withAutowiring(true) to restore the previous behavior.
Factory params are no longer resolved by name. Replace static fn (string $mail) => ... with static fn (ContainerInterface $c) => ... $c->get('mail'), or pass the value to create().
Containers returned by withEntry(), withAutowiring() and withDelegate() no longer share resolved instances with the original container. Services are rebuilt with the new configuration.
get(Container::class) on such a container returns the new container, not the original one.
has() returns false for classes that cannot be instantiated (abstract classes, private constructors).
Exception classes are final.
NotInstantiableException implements NotFoundExceptionInterface.
A missing dependency inside a factory throws a DependencyException instead of letting the inner NotFoundException bubble up.
Variadic params are no longer autowired. Pass them explicitly as an array.

semperton / container

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