When\When::prepareOccurrences PHP Method

    protected function prepareOccurrences($occurrences, $count = 0)
    {
        if (isset($this->bysetpos)) {
            $filtered_occurrences = array();
            if ($count > 0) {
                $occurrenceCount = count($occurrences);
                foreach ($this->bysetpos as $setpos) {
                    if ($setpos > 0 && isset($occurrences[$setpos - 1])) {
                        $filtered_occurrences[] = $occurrences[$setpos - 1];
                    } elseif (isset($occurrences[$occurrenceCount + $setpos])) {
                        $filtered_occurrences[] = $occurrences[$occurrenceCount + $setpos];
                    }
                }
            }
            $occurrences = $filtered_occurrences;
        }
        return $occurrences;
    }