One solution is to upgrade to [PHP 7][1], but see the note in the manual:

>**THIS IS A DEVELOPMENT PREVIEW - DO NOT USE IT IN PRODUCTION!**


The reason why you get this error can be found in the manual page of [`dirname()`][2], under changelog:

> ###Changelog

>     Version 	Description
>     7.0.0 	Added the optional levels parameter.


  [1]: http://php.net/archive/2015.php#id2015-09-17-2
  [2]: http://php.net/manual/en/function.dirname.php#refsect1-function.dirname-changelog