Iterator::key() as object

    class b implements Iterator
    {
        private $p  = 0;
        private $d  = [];

        function add($o1, $o2)
        {
            $this->d[] = [$o1, $o2];
        }

        function key()
        {
            return $this->d[$this->p][0];
        }

        function rewind()
        {
            $this->p = 0;
        }

        function current()
        {
            return $this->d[$this->p][1];
        }

        function next()
        {
            ++$this->p;
        }


        function valid()
        {
            return isset($this->d[$this->p]);
        }

    }

    $b = new b;
    $b->add(new Str, new Str);


    foreach($b as $k => $v)
        var_dump($k); // object Str