PSR-11

container.php

<?php

use Psr\Container\ContainerInterface;

class AppContainer implements ContainerInterface {

	private array $instances = [];

	public function get( string $id ) {
		if ( $this->has( $id ) ) {
			return $this->instances[ $id ];
		}

		try {
			$instance = $this->createObject( $id );
		} catch ( \ReflectionException $e ) {
			return $e;
		}

		$this->instances[ $id ] = $instance;

		return $instance;
	}

	public function has( string $id ): bool {
		return isset( $this->instances[ $id ] );
	}

	/**
	 * Create Object.
	 *
	 * @param  string  $className
	 *
	 * @return mixed|object|\ReflectionException|string|null
	 */
	private function createObject( string $className ) {
		// If this class exists or not
		if ( ! class_exists( $className ) ) {
			return new \ReflectionException( '404', "Class: {$className} doesn't exists." );
		}

		// If the class has a constructor or not.
		$reflection = new \ReflectionClass( $className );
		if ( null === $reflection->getConstructor() ) {
			return new $className;
		}

		// Get all the parameters.
		$parameters = $reflection->getConstructor()->getParameters();

		try {
			$dependencies = $this->buildDependencies( $parameters );
		} catch ( \ReflectionException $e ) {
			return $e;
		}

		try {
			return $reflection->newInstanceArgs( $dependencies );
		} catch ( \ReflectionException $e ) {
			return $e;
		}
	}

	/**
	 * Build Dependencies.
	 *
	 * @param  ReflectionParameter[]  $parameters
	 *
	 * @return array
	 */
	private function buildDependencies( array $parameters ): array {
		$dependencies = [];
		foreach ( $parameters as $parameter ) {
			$dependencies[] = $this->createObject( $parameter->getClass()->getName() );
		}

		return $dependencies;
	}

}

Class Car {


	private Engine $engine;

	public function __construct(Engine $engine) {
		$this->engine = $engine;
	}

	public function getCar(): string {
		return 'Car with ' . $this->getEngine();
	}

	public function getEngine(): string {
		return $this->engine->getName();
	}
}




Class Engine {

	private string $name;

	public function __construct() {
		$this->name = 'v8 Engine';
	}

	public function getName(): string {
		return $this->name;
	}
}

// Use
$car = new Car(new Engine());
echo $car->getCar();
echo PHP_EOL;
die();

// Use with PSR-11
$container = new AppContainers();
try {
    $app = $container->get( Car::class );
    $car  = $app->get(Vehicle::class);
    echo $car->getCar();
    echo PHP_EOL;
} catch ( NotFoundExceptionInterface|ContainerExceptionInterface $e ) {
    echo $e->getMessage();
    die($e->getCode());
}


// In composer.json

"psr/container": "^2.0"

// or,
composer require psr/container

// Useful link
https://www.php-fig.org/psr/psr-11/