Since PHP 5.5.X foreach can accept non scalar items. So the return can be anything ;)
(PHP 5 >= 5.0.0, PHP 7)
Iterator::key — Return the key of the current element
Returns the key of the current element.
This function has no parameters.
Returns scalar on success, or NULL on failure.
Issues E_NOTICE on failure.
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;
}
Be careful, the returned value must be a scalar! Took me a while to figure out why foreach() doesn't work on my class that handles arrays with object keys...