Bob\FileTask::getTimestamp PHP Method

    function getTimestamp()
    {
        $lastModifiedTimes = iterator_to_array(itertools\filter(itertools\map(function ($file) {
            if (file_exists($file)) {
                return @filemtime($file);
            }
        }, $this->prerequisites)));
        if ($lastModifiedTimes) {
            return max($lastModifiedTimes);
        }
        return 0;
    }