<?php
class Bar {
    public function __construct(
        public Bar $bar,
        public int $x,
    ) {}

    public function with(): self
    {
        return clone $this;
    }
}

class Fiz {
    public mixed $cache = null;

    public function foo(int $i)
    {
        if (!$this->cache) {
            $this->cache = $this->factor($i);
        }

        if ($i <= 1) {
            return $this->cache->with();
        }

        return $this->cache;
    }

    public function factor(int $i): object
    {
        $reflector = new ReflectionClass(Bar::class);

        return $reflector->newLazyGhost(
            function (Bar $bar) use ($i) {
                $bar->__construct($this->foo($i + 1), 2);
            },
        );
    }
}

$fiz = new Fiz();

$f = $fiz->foo(0);
var_dump($f->bar->bar->x);