app\models\UserAccount::removeUserId PHP Method

    public function removeUserId($userId)
    {
        if (!$userId || !self::hasUserId($userId)) {
            return;
        }
        for ($i = 1; $i <= 5; $i++) {
            $field = "user_id{$i}";
            if ($this->{$field} && $this->{$field} == $userId) {
                $this->{$field} = null;
            }
        }
    }