Piwik\DataTable\Row::getColumnValuesMerged PHP Method

    private function getColumnValuesMerged($operation, $thisColumnValue, $columnToSumValue, $thisRow, $rowToSum)
    {
        switch ($operation) {
            case 'skip':
                $newValue = null;
                break;
            case 'max':
                $newValue = max($thisColumnValue, $columnToSumValue);
                break;
            case 'min':
                if (!$thisColumnValue) {
                    $newValue = $columnToSumValue;
                } elseif (!$columnToSumValue) {
                    $newValue = $thisColumnValue;
                } else {
                    $newValue = min($thisColumnValue, $columnToSumValue);
                }
                break;
            case 'sum':
                $newValue = $this->sumRowArray($thisColumnValue, $columnToSumValue);
                break;
            case 'uniquearraymerge':
                if (is_array($thisColumnValue) && is_array($columnToSumValue)) {
                    foreach ($columnToSumValue as $columnSum) {
                        if (!in_array($columnSum, $thisColumnValue)) {
                            $thisColumnValue[] = $columnSum;
                        }
                    }
                } elseif (!is_array($thisColumnValue) && is_array($columnToSumValue)) {
                    $thisColumnValue = $columnToSumValue;
                }
                $newValue = $thisColumnValue;
                break;
            default:
                if (is_callable($operation)) {
                    return call_user_func($operation, $thisColumnValue, $columnToSumValue, $thisRow, $rowToSum);
                }
                throw new Exception("Unknown operation '{$operation}'.");
        }
        return $newValue;
    }