chickenEggOop.php

<?php

interface Fowl
{
    public function layEgg() : Egg;
}

class Egg
{
    private $hatched;
    private $type;
    
    public function __construct(string $fowlType)
    {
        $this->type = $fowlType;

    }

    public function hatch() : ?Fowl
    {
        if ($this->hatched == true) {
            throw new Exception('Already htached');
        }
        
        $this->hatched = true;
            
        return new $this->type();
    }
}

class Hen implements Fowl
{
    public function layEgg() : Egg {
        return new Egg('Hen');
    }
}