Ping backable fails PHP lint

[Dunhamzzz]

Seems like the PingBackable behaviour wasn't tested, at least through lint:

php -l PingbackableBehavior.php
PHP Fatal error: Can't use function return value in write context in PingbackableBehavior.php on line 63
Errors parsing PingbackableBehavior.php

Unfortunately I don't use this part of the Utils plugin so I haven't really looked through it much yet.