minimal di-container

Container.php

<?php

class Container {
	public $config;

	public $cache = [];

	public function __construct($config)
	{
		$this->config = $config;
		$this->checkConflicts($config);
	}

	protected function checkAgainst($class, $params)
	{
		if (is_array($params)) {
			foreach ($params as $check) {
				if ($check === $class) {
					throw new LogicException("conflicts in the config for {$class}");
				}
	
				if (isset($this->config[$check])) {
					$this->checkAgainst($class, $this->config[$check]);
				}
			}
		}
	}

	public function checkConflicts($config)
	{
		foreach ($config as $class => $params) {
			$this->checkAgainst($class, $params);
		}
	}

	public function get($class)
	{
		if (isset($this->cache[$class])) { // cached
			return $this->cache[$class];
		}

		if (!isset($this->config[$class])) {
			throw new InvalidArgumentException("{$class} does not exists in config");
		}

		$aParams = [];
		foreach ($this->config[$class] as $param) {
			if (is_string($param) && class_exists($param)) {
				if ($param === $class) {
					throw new LogicException("you can't require the same class as parameter");
				}

				$aParams[] = $this->get($param);
				continue;
			}

			$aParams[] = $param;
		}

		$this->cache[$class] = new $class(...$aParams);

		return $this->cache[$class];
	}

	public function has($class)
	{
		return isset($this->config[$class]);
	}
}

index.php

<?php

$container = new Container([ // config, key value: class => parameters[]
	FooBar::class => [],
	Bar::class => [FooBar::class],
	Foo::class => [Bar::class]
]);

$foo = $container->get(Foo::class); // Foo
echo get_class($foo->bar) // Bar