Iterator::key

(PHP 5, PHP 7)

返回当前元素的键

说明

abstractpublicIterator::key(void): scalar

返回当前元素的键。

参数

此函数没有参数。

返回值

成功返回标量，失败则返回NULL。

错误／异常

失败时分发E_NOTICE级错误。

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;
  }