Iterator::key

Since PHP 5.5.X foreach can accept non scalar items. So the return can be anything ;)

And converts everything to integer except string, so in php the post process could be:    public function key() {        $yourKey = $this->createYourKey();        if (is_object($yourKey) || is_array($yourKey))            throw new Exception('Array and Object not allowed.');        elseif (is_string($yourKey))            return $yourKey;        else            return (int) $yourKey;    }

This function may return any type, not just scalar, for some Iterator types. In particular, it is very trivial to write a generator function that yields arbitrary keys:<?phpfunction foo() {  yield null => 1;  yield new stdclass => 2;}?>