Fixed #848 // Others PHP 8.1 compatibility bugs

Author: Geolim4

lib/Phpfastcache/Core/Item/ItemExtendedTrait.php

@@ -336,6 +336,7 @@ public function getDataAsJsonString(int $option = 0, int $depth = 512): string
      * Implements \JsonSerializable interface
      * @return mixed
      */
+    #[\ReturnTypeWillChange] // PHP 8.1 compatibility
     public function jsonSerialize()
     {
         return $this->get();

lib/Phpfastcache/Util/ArrayObject.php

@@ -49,6 +49,7 @@ public function __construct(...$args)
     /**
      * @return mixed
      */
+    #[\ReturnTypeWillChange] // PHP 8.1 compatibility
     public function current()
     {
         return $this->array[$this->position];
@@ -107,7 +108,7 @@ public function count(): int
      * @param mixed $offset
      * @return mixed
      */
-    #[\ReturnTypeWillChange] // PHP 8 compatibility
+    #[\ReturnTypeWillChange] // PHP 8.1 compatibility
     public function offsetGet($offset)
     {
         return $this->array[$offset] ?? null;