diff --git a/CRM/Core/Payment/OmnipayMultiProcessor.php b/CRM/Core/Payment/OmnipayMultiProcessor.php
index 2b933e70e..7d55c2826 100644
--- a/CRM/Core/Payment/OmnipayMultiProcessor.php
+++ b/CRM/Core/Payment/OmnipayMultiProcessor.php
@@ -82,7 +82,18 @@ class CRM_Core_Payment_OmnipayMultiProcessor extends CRM_Core_Payment_PaymentExt
    * @var \Civi\Payment\PropertyBag
    */
   protected $propertyBag;
-
+  
+  /**
+   * For PHP8.1
+   * https://www.php.net/manual/en/language.oop5.magic.php#object.serialize
+   * @return array
+   */
+  public function __serialize(): array {
+    $data = (object) get_object_vars($this);
+    $this->cleanupObjectForSerialization($data, TRUE);
+    return (array) $data;
+  }
+  
   /**
    * Serialize, first removing gateway
    *
@@ -91,8 +102,7 @@ class CRM_Core_Payment_OmnipayMultiProcessor extends CRM_Core_Payment_PaymentExt
    * @return string
    */
   public function serialize(): string {
-    $this->cleanupClassForSerialization(TRUE);
-    return serialize(get_object_vars($this));
+    return serialize($this->serialize());
   }
 
   /**
@@ -104,7 +114,17 @@ public function serialize(): string {
    */
   public function unserialize($data) {
     $values = unserialize($data);
-    foreach ($values as $key => $value) {
+    $this->__unserialize($values);
+  }
+
+  /**
+   * For PHP8.1
+   * https://www.php.net/manual/en/language.oop5.magic.php#object.unserialize
+   * 
+   * @param array $data
+   */
+  public function __unserialize(array $data): void {
+    foreach ($data as $key => $value) {
       $this->$key = $value;
     }
   }
diff --git a/CRM/Core/Payment/PaymentExtended.php b/CRM/Core/Payment/PaymentExtended.php
index 0093023cc..2872655a4 100644
--- a/CRM/Core/Payment/PaymentExtended.php
+++ b/CRM/Core/Payment/PaymentExtended.php
@@ -381,6 +381,25 @@ public function serialize() {
     return serialize($this);
   }
 
+  /**
+   * Unset various objects that will fail to serialize when the form is stored to session.
+   *
+   * @param object $object (by reference)
+   * @param bool $isIncludeGateWay Should we also unset the gateway.
+   */
+  protected function cleanupObjectForSerialization(&$object, $isIncludeGateWay = FALSE) {
+    if (\Civi::settings()->get('omnipay_developer_mode') && !empty($object->history)) {
+      $object->logHttpTraffic(FALSE);
+    }
+    $object->history = [];
+    $object->client = NULL;
+    $object->lock = NULL;
+    $object->guzzleClient = NULL;
+    if ($isIncludeGateWay) {
+      $object->gateway = NULL;
+    }
+  }
+
   /**
    * Unset various objects that will fail to serialize when the form is stored to session.
    *
@@ -388,17 +407,9 @@ public function serialize() {
    *   Should we also unset the gateway.
    *   (possibly the default here should be TRUE but we want to be sure we are not
    *   unsetting it when it is still being used.)
+   *   For retro-compatibilty, this still transforms the current entity.
    */
   protected function cleanupClassForSerialization($isIncludeGateWay = FALSE) {
-    if (\Civi::settings()->get('omnipay_developer_mode') && !empty($this->history)) {
-      $this->logHttpTraffic(FALSE);
-    }
-    $this->history = [];
-    $this->client = NULL;
-    $this->lock = NULL;
-    $this->guzzleClient = NULL;
-    if ($isIncludeGateWay) {
-      $this->gateway = NULL;
-    }
+    $this->cleanupObjectForSerialization($this, $isIncludeGateWay);
   }
 }