app\models\UserDonation::totalLength PHP Method

    public static function totalLength($userId)
    {
        $lengths = static::where('target_user_id', $userId)->select('cancel', DB::raw('SUM(length) as length'))->groupBy('cancel')->get();
        $totalLength = 0;
        foreach ($lengths as $length) {
            if ($length->cancel !== true) {
                $totalLength += $length->length;
            } else {
                $totalLength -= $length->length;
            }
        }
        return $totalLength;
    }