src/QUI/Memberships/Users/Handler.php

@@ -13,6 +13,8 @@
 use QUI\Memberships\Utils;
 use QUI\Permissions\Permission;
 
+use function is_string;
+
 class Handler extends Factory
 {
     /**
@@ -222,7 +224,7 @@ public function getIdsByMembershipId(int $membershipId, bool $includeArchived =
      */
     public function getMembershipUsersByUserId(int | string $userId, bool $includeArchived = false): array
     {
-        if (is_int($userId)) {
+        if (is_string($userId)) {
             try {
                 $userId = QUI::getUsers()->get($userId)->getId();
             } catch (QUI\Exception) {

src/QUI/Memberships/Users/MembershipUser.php

@@ -951,11 +951,11 @@ public function getHistory(): array
     /**
      * Format date based on User Locale and duration mode
      *
-     * @param DateTime|string $date - Formatted date YYYY-MM-DD HH:MM:SS or \DateTime object
+     * @param DateTime|string|null $date - Formatted date YYYY-MM-DD HH:MM:SS or \DateTime object
      * @return string|false - formatted date or false on error
      * @throws Exception
      */
-    protected function formatDate(DateTime | string $date): bool | string
+    protected function formatDate(DateTime | string | null $date): bool | string
     {
         if (empty($date) || $date === '0000-00-00 00:00:00') {
             return false;