Incompatible with RecursiveIterator

#4517

http://php.net/manual/en/recursiveiterator.haschildren.php
> Returns TRUE if the current entry can be iterated over, otherwise returns FALSE. 
I'm sorry, I couldn't find the rule last night.
I will read PSR-2 more carefully later.
 https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md