<?php

declare(strict_types=1);

use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Reference;

require_once __DIR__ . '/vendor/autoload.php';

interface Salute
{
    public function salute(): string;
}

class Foo implements Salute
{
    private $bar;

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

    public function salute(): string
    {
        return $this->bar->salute();
    }
}

class Bar implements Salute
{
    public function salute(): string
    {
        return "Hello world!";
    }
}

$container = new ContainerBuilder();

$container->register(Foo::class, Foo::class)->addArgument(new Reference(Bar::class))->setPublic(true);
$container->register(Bar::class, Bar::class);

$container->compile();

echo $container->get(Foo::class)->salute().PHP_EOL;