gistfile1.php

<?php

namespace Yolo;

class ServiceNotFoundException extends \RuntimeException {}
class RecursiveServiceDefinitionException extends \RuntimeException {}
class InvalidArgumentException extends \RuntimeException {}

class Container
{
    private $definitions = [];
    private $instances = [];

    function __construct(array $definitions)
    {
        $this->definitions = $definitions;
    }

    function get($name)
    {
        if (isset($this->instances[$name])) {
            return $this->instances[$name];
        }

        if (!isset($this->definitions[$name])) {
            throw new ServiceNotFoundException($name);
        }

        $definition = $this->definitions[$name];
        $instance = $this->createInstance($name, $definition);
        $this->instances[$name] = $instance;

        return $instance;
    }

    private function createInstance($name, $definition)
    {
        $class = $definition['class'];
        $arguments = isset($definition['arguments']) ? $definition['arguments'] : [];

        $resolvedArgs = array_map([$this, 'resolveArgument'], $arguments);

        $reflection = new \ReflectionClass($class);
        return $reflection->newInstanceArgs($resolvedArgs);
    }

    private function resolveArgument(array $arg)
    {
        if (isset($arg['ref'])) {
            return $this->get($arg['ref']);
        }

        if (isset($arg['value'])) {
            return $arg['value'];
        }

        throw new InvalidArgumentException(sprintf('Got invalid service argument %s', json_encode($arg)));
    }
}

namespace _;

use Yolo\Container;
use Yolo\RecursiveServiceDefinitionException;

class Foo
{
    public $bar;

    function __construct(Bar $bar)
    {
        $this->bar = $bar;
    }
}

class Bar {}

class Baz {
    public $name;

    function __construct($name)
    {
        $this->name = $name;
    }
}

$container = new Container([
    'foo' => [
        'class'     => '_\Foo',
        'arguments' => [['ref' => 'bar']],
    ],
    'bar' => [
        'class' => '_\Bar',
    ],
    'baz' => [
        'class'     => '_\Baz',
        'arguments' => [['value' => 'baz']],
    ],
]);

var_dump($container->get('foo'));
var_dump($container->get('bar'));
var_dump($container->get('baz'));