diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
index 653d7c3268e..fb06ee5555f 100644
--- a/.php-cs-fixer.dist.php
+++ b/.php-cs-fixer.dist.php
@@ -63,6 +63,8 @@
         'no_trailing_whitespace_in_comment' => true,
         // Remove trailing whitespace at the end of blank lines.
         'no_whitespace_in_blank_line' => true,
+        // Adds or removes ? before single type declarations or |null at the end of union types when parameters have a default null value.
+        'nullable_type_declaration_for_default_null_value' => true,
         // Orders the elements of classes/interfaces/traits.
         'ordered_class_elements' => false,
         // Ordering `use` statements.
diff --git a/app/code/core/Mage/Admin/Model/Acl/Assert/Ip.php b/app/code/core/Mage/Admin/Model/Acl/Assert/Ip.php
index cc524a2a7c5..ca25cbe4125 100644
--- a/app/code/core/Mage/Admin/Model/Acl/Assert/Ip.php
+++ b/app/code/core/Mage/Admin/Model/Acl/Assert/Ip.php
@@ -32,8 +32,8 @@ class Mage_Admin_Model_Acl_Assert_Ip implements Zend_Acl_Assert_Interface
      */
     public function assert(
         Mage_Admin_Model_Acl $acl,
-        Mage_Admin_Model_Acl_Role $role = null,
-        Mage_Admin_Model_Acl_Resource $resource = null,
+        ?Mage_Admin_Model_Acl_Role $role = null,
+        ?Mage_Admin_Model_Acl_Resource $resource = null,
         $privilege = null
     ) {
         return $this->_isCleanIP(Mage::helper('core/http')->getRemoteAddr());
diff --git a/app/code/core/Mage/Admin/Model/Acl/Assert/Time.php b/app/code/core/Mage/Admin/Model/Acl/Assert/Time.php
index f82ad8394e8..e69d46c8529 100644
--- a/app/code/core/Mage/Admin/Model/Acl/Assert/Time.php
+++ b/app/code/core/Mage/Admin/Model/Acl/Assert/Time.php
@@ -32,8 +32,8 @@ class Mage_Admin_Model_Acl_Assert_Time implements Zend_Acl_Assert_Interface
      */
     public function assert(
         Mage_Admin_Model_Acl $acl,
-        Mage_Admin_Model_Acl_Role $role = null,
-        Mage_Admin_Model_Acl_Resource $resource = null,
+        ?Mage_Admin_Model_Acl_Role $role = null,
+        ?Mage_Admin_Model_Acl_Resource $resource = null,
         $privilege = null
     ) {
         return $this->_isCleanTime(time());
diff --git a/app/code/core/Mage/Admin/Model/Redirectpolicy.php b/app/code/core/Mage/Admin/Model/Redirectpolicy.php
index 8782ca92853..85a501d22d9 100644
--- a/app/code/core/Mage/Admin/Model/Redirectpolicy.php
+++ b/app/code/core/Mage/Admin/Model/Redirectpolicy.php
@@ -45,7 +45,7 @@ public function __construct($parameters = [])
      */
     public function getRedirectUrl(
         Mage_Admin_Model_User $user,
-        Zend_Controller_Request_Http $request = null,
+        ?Zend_Controller_Request_Http $request = null,
         $alternativeUrl = null
     ) {
         if (empty($request)) {
diff --git a/app/code/core/Mage/Admin/Model/Roles.php b/app/code/core/Mage/Admin/Model/Roles.php
index 142f9dd2a71..9ecda32e68d 100644
--- a/app/code/core/Mage/Admin/Model/Roles.php
+++ b/app/code/core/Mage/Admin/Model/Roles.php
@@ -123,7 +123,7 @@ public function getRoleUsers()
      * @return Varien_Simplexml_Element|false|array
      */
     protected function _buildResourcesArray(
-        Varien_Simplexml_Element $resource = null,
+        ?Varien_Simplexml_Element $resource = null,
         $parentName = null,
         $level = 0,
         $represent2Darray = null,
diff --git a/app/code/core/Mage/Adminhtml/Block/Catalog/Product/Composite/Configure.php b/app/code/core/Mage/Adminhtml/Block/Catalog/Product/Composite/Configure.php
index 7bae1cec612..d15d4a6b5a3 100644
--- a/app/code/core/Mage/Adminhtml/Block/Catalog/Product/Composite/Configure.php
+++ b/app/code/core/Mage/Adminhtml/Block/Catalog/Product/Composite/Configure.php
@@ -54,7 +54,7 @@ public function getProduct()
      * @param Mage_Catalog_Model_Product|null $product
      * @return $this
      */
-    public function setProduct(Mage_Catalog_Model_Product $product = null)
+    public function setProduct(?Mage_Catalog_Model_Product $product = null)
     {
         $this->_product = $product;
         return $this;
diff --git a/app/code/core/Mage/Adminhtml/Controller/Action.php b/app/code/core/Mage/Adminhtml/Controller/Action.php
index d15e426e4ba..ec3fd52958d 100644
--- a/app/code/core/Mage/Adminhtml/Controller/Action.php
+++ b/app/code/core/Mage/Adminhtml/Controller/Action.php
@@ -367,7 +367,7 @@ protected function _redirect($path, $arguments = [])
         return $this;
     }
 
-    protected function _forward($action, $controller = null, $module = null, array $params = null)
+    protected function _forward($action, $controller = null, $module = null, ?array $params = null)
     {
         $this->_getSession()->setIsUrlNotice($this->getFlag('', self::FLAG_IS_URLS_CHECKED));
         return parent::_forward($action, $controller, $module, $params);
diff --git a/app/code/core/Mage/Adminhtml/Helper/Config.php b/app/code/core/Mage/Adminhtml/Helper/Config.php
index 5e9c75a6bea..5e29f965338 100644
--- a/app/code/core/Mage/Adminhtml/Helper/Config.php
+++ b/app/code/core/Mage/Adminhtml/Helper/Config.php
@@ -31,7 +31,7 @@ class Mage_Adminhtml_Helper_Config extends Mage_Core_Helper_Abstract
      * @param string $inputType
      * @return array
      */
-    public function getInputTypes(string $inputType = null): array
+    public function getInputTypes(?string $inputType = null): array
     {
         $inputTypes = [
             'color' => [
diff --git a/app/code/core/Mage/Adminhtml/Model/System/Config/Source/Admin/Page.php b/app/code/core/Mage/Adminhtml/Model/System/Config/Source/Admin/Page.php
index e7e65b40788..e79b3daedc4 100644
--- a/app/code/core/Mage/Adminhtml/Model/System/Config/Source/Admin/Page.php
+++ b/app/code/core/Mage/Adminhtml/Model/System/Config/Source/Admin/Page.php
@@ -70,7 +70,7 @@ protected function _getUrlModel()
         return $this->_url;
     }
 
-    protected function _buildMenuArray(Varien_Simplexml_Element $parent = null, $path = '', $level = 0)
+    protected function _buildMenuArray(?Varien_Simplexml_Element $parent = null, $path = '', $level = 0)
     {
         if (is_null($parent)) {
             $parent = Mage::getSingleton('admin/config')->getAdminhtmlConfig()->getNode('menu');
diff --git a/app/code/core/Mage/Api/Model/Acl/Assert/Ip.php b/app/code/core/Mage/Api/Model/Acl/Assert/Ip.php
index 9cd4279cba0..189c550dadc 100644
--- a/app/code/core/Mage/Api/Model/Acl/Assert/Ip.php
+++ b/app/code/core/Mage/Api/Model/Acl/Assert/Ip.php
@@ -32,8 +32,8 @@ class Mage_Api_Model_Acl_Assert_Ip implements Zend_Acl_Assert_Interface
      */
     public function assert(
         Mage_Api_Model_Acl $acl,
-        Mage_Api_Model_Acl_Role $role = null,
-        Mage_Api_Model_Acl_Resource $resource = null,
+        ?Mage_Api_Model_Acl_Role $role = null,
+        ?Mage_Api_Model_Acl_Resource $resource = null,
         $privilege = null
     ) {
         return $this->_isCleanIP(Mage::helper('core/http')->getRemoteAddr());
diff --git a/app/code/core/Mage/Api/Model/Acl/Assert/Time.php b/app/code/core/Mage/Api/Model/Acl/Assert/Time.php
index 31e2df3faef..903cbe17030 100644
--- a/app/code/core/Mage/Api/Model/Acl/Assert/Time.php
+++ b/app/code/core/Mage/Api/Model/Acl/Assert/Time.php
@@ -32,8 +32,8 @@ class Mage_Api_Model_Acl_Assert_Time implements Zend_Acl_Assert_Interface
      */
     public function assert(
         Mage_Api_Model_Acl $acl,
-        Mage_Api_Model_Acl_Role $role = null,
-        Mage_Api_Model_Acl_Resource $resource = null,
+        ?Mage_Api_Model_Acl_Role $role = null,
+        ?Mage_Api_Model_Acl_Resource $resource = null,
         $privilege = null
     ) {
         return $this->_isCleanTime(time());
diff --git a/app/code/core/Mage/Api/Model/Roles.php b/app/code/core/Mage/Api/Model/Roles.php
index bedc0e43c2a..d73dd218a3e 100644
--- a/app/code/core/Mage/Api/Model/Roles.php
+++ b/app/code/core/Mage/Api/Model/Roles.php
@@ -108,7 +108,7 @@ public function getRoleUsers()
      * @return array|false|Varien_Simplexml_Element
      */
     protected function _buildResourcesArray(
-        Varien_Simplexml_Element $resource = null,
+        ?Varien_Simplexml_Element $resource = null,
         $parentName = null,
         $level = 0,
         $represent2Darray = null,
diff --git a/app/code/core/Mage/Api2/Model/Route/ApiType.php b/app/code/core/Mage/Api2/Model/Route/ApiType.php
index 8975ff07c59..6ffd07566bc 100644
--- a/app/code/core/Mage/Api2/Model/Route/ApiType.php
+++ b/app/code/core/Mage/Api2/Model/Route/ApiType.php
@@ -42,7 +42,7 @@ public function __construct(
         $route,
         $defaults = [],
         $reqs = [],
-        Zend_Translate $translator = null,
+        ?Zend_Translate $translator = null,
         $locale = null
     ) {
         parent::__construct([Mage_Api2_Model_Route_Abstract::PARAM_ROUTE => str_replace('.php', '', basename(getenv('SCRIPT_FILENAME'))) . '/:api_type']);
diff --git a/app/code/core/Mage/Catalog/Block/Product/View/Options.php b/app/code/core/Mage/Catalog/Block/Product/View/Options.php
index 63f8dbfd6a0..ab9cecd8499 100644
--- a/app/code/core/Mage/Catalog/Block/Product/View/Options.php
+++ b/app/code/core/Mage/Catalog/Block/Product/View/Options.php
@@ -61,7 +61,7 @@ public function getProduct()
      * @param Mage_Catalog_Model_Product|null $product
      * @return $this
      */
-    public function setProduct(Mage_Catalog_Model_Product $product = null)
+    public function setProduct(?Mage_Catalog_Model_Product $product = null)
     {
         $this->_product = $product;
         return $this;
diff --git a/app/code/core/Mage/Catalog/Block/Product/View/Options/Abstract.php b/app/code/core/Mage/Catalog/Block/Product/View/Options/Abstract.php
index 8d52a32d6a2..559c59b6495 100644
--- a/app/code/core/Mage/Catalog/Block/Product/View/Options/Abstract.php
+++ b/app/code/core/Mage/Catalog/Block/Product/View/Options/Abstract.php
@@ -41,7 +41,7 @@ abstract class Mage_Catalog_Block_Product_View_Options_Abstract extends Mage_Cor
      * @param Mage_Catalog_Model_Product|null $product
      * @return $this
      */
-    public function setProduct(Mage_Catalog_Model_Product $product = null)
+    public function setProduct(?Mage_Catalog_Model_Product $product = null)
     {
         $this->_product = $product;
         return $this;
diff --git a/app/code/core/Mage/Catalog/Model/Product/Compare/Item.php b/app/code/core/Mage/Catalog/Model/Product/Compare/Item.php
index 8b5c9cc802a..f7d95c4748e 100644
--- a/app/code/core/Mage/Catalog/Model/Product/Compare/Item.php
+++ b/app/code/core/Mage/Catalog/Model/Product/Compare/Item.php
@@ -177,7 +177,7 @@ public function bindCustomerLogin()
      * @param Varien_Event_Observer|null $observer
      * @return $this
      */
-    public function bindCustomerLogout(Varien_Event_Observer $observer = null)
+    public function bindCustomerLogout(?Varien_Event_Observer $observer = null)
     {
         $this->_getResource()->purgeVisitorByCustomer($this);
 
diff --git a/app/code/core/Mage/Catalog/Model/Product/Option.php b/app/code/core/Mage/Catalog/Model/Product/Option.php
index e58a6a07b9b..edf72c02fa6 100644
--- a/app/code/core/Mage/Catalog/Model/Product/Option.php
+++ b/app/code/core/Mage/Catalog/Model/Product/Option.php
@@ -262,7 +262,7 @@ public function getProduct()
      * @param Mage_Catalog_Model_Product|null $product
      * @return $this
      */
-    public function setProduct(Mage_Catalog_Model_Product $product = null)
+    public function setProduct(?Mage_Catalog_Model_Product $product = null)
     {
         $this->_product = $product;
         return $this;
diff --git a/app/code/core/Mage/Catalog/Model/Resource/Category/Indexer/Product.php b/app/code/core/Mage/Catalog/Model/Resource/Category/Indexer/Product.php
index dfe5ac24438..286e83a1be5 100644
--- a/app/code/core/Mage/Catalog/Model/Resource/Category/Indexer/Product.php
+++ b/app/code/core/Mage/Catalog/Model/Resource/Category/Indexer/Product.php
@@ -311,7 +311,7 @@ public function catalogCategorySave(Mage_Index_Model_Event $event)
      * @return $this
      * @throws Zend_Db_Adapter_Exception
      */
-    protected function _refreshNotAnchorRootCategories(array $categoryIds = null)
+    protected function _refreshNotAnchorRootCategories(?array $categoryIds = null)
     {
         if (empty($categoryIds)) {
             return $this;
diff --git a/app/code/core/Mage/CatalogIndex/Model/Indexer/Eav.php b/app/code/core/Mage/CatalogIndex/Model/Indexer/Eav.php
index c9d17d2bf95..bb59b2a7712 100644
--- a/app/code/core/Mage/CatalogIndex/Model/Indexer/Eav.php
+++ b/app/code/core/Mage/CatalogIndex/Model/Indexer/Eav.php
@@ -42,7 +42,7 @@ protected function _construct()
      * @param Mage_Eav_Model_Entity_Attribute_Abstract|null $attribute
      * @return array
      */
-    public function createIndexData(Mage_Catalog_Model_Product $object, Mage_Eav_Model_Entity_Attribute_Abstract $attribute = null)
+    public function createIndexData(Mage_Catalog_Model_Product $object, ?Mage_Eav_Model_Entity_Attribute_Abstract $attribute = null)
     {
         $data = [];
 
diff --git a/app/code/core/Mage/CatalogIndex/Model/Indexer/Interface.php b/app/code/core/Mage/CatalogIndex/Model/Indexer/Interface.php
index 4f15b9cc1cd..82b4cf55a92 100644
--- a/app/code/core/Mage/CatalogIndex/Model/Indexer/Interface.php
+++ b/app/code/core/Mage/CatalogIndex/Model/Indexer/Interface.php
@@ -24,5 +24,5 @@ interface Mage_CatalogIndex_Model_Indexer_Interface
      * @param Mage_Eav_Model_Entity_Attribute_Abstract|null $attribute
      * @return mixed
      */
-    public function createIndexData(Mage_Catalog_Model_Product $object, Mage_Eav_Model_Entity_Attribute_Abstract $attribute = null);
+    public function createIndexData(Mage_Catalog_Model_Product $object, ?Mage_Eav_Model_Entity_Attribute_Abstract $attribute = null);
 }
diff --git a/app/code/core/Mage/CatalogIndex/Model/Indexer/Minimalprice.php b/app/code/core/Mage/CatalogIndex/Model/Indexer/Minimalprice.php
index ec510f88593..07fd53d56d0 100644
--- a/app/code/core/Mage/CatalogIndex/Model/Indexer/Minimalprice.php
+++ b/app/code/core/Mage/CatalogIndex/Model/Indexer/Minimalprice.php
@@ -90,7 +90,7 @@ public function getPriceAttribute()
      * @param Mage_Eav_Model_Entity_Attribute_Abstract|null $attribute
      * @return array|bool
      */
-    public function createIndexData(Mage_Catalog_Model_Product $object, Mage_Eav_Model_Entity_Attribute_Abstract $attribute = null)
+    public function createIndexData(Mage_Catalog_Model_Product $object, ?Mage_Eav_Model_Entity_Attribute_Abstract $attribute = null)
     {
         $searchEntityId = $object->getId();
         $priceAttributeId = $this->getTierPriceAttribute()->getId();
diff --git a/app/code/core/Mage/CatalogIndex/Model/Indexer/Price.php b/app/code/core/Mage/CatalogIndex/Model/Indexer/Price.php
index d76264b0328..04715b9e455 100644
--- a/app/code/core/Mage/CatalogIndex/Model/Indexer/Price.php
+++ b/app/code/core/Mage/CatalogIndex/Model/Indexer/Price.php
@@ -55,7 +55,7 @@ protected function _construct()
      * @param Mage_Eav_Model_Entity_Attribute_Abstract|null $attribute
      * @return array
      */
-    public function createIndexData(Mage_Catalog_Model_Product $object, Mage_Eav_Model_Entity_Attribute_Abstract $attribute = null)
+    public function createIndexData(Mage_Catalog_Model_Product $object, ?Mage_Eav_Model_Entity_Attribute_Abstract $attribute = null)
     {
         $data = [];
 
diff --git a/app/code/core/Mage/CatalogIndex/Model/Indexer/Tierprice.php b/app/code/core/Mage/CatalogIndex/Model/Indexer/Tierprice.php
index 1aaa79c16d5..f3f4fd3edb7 100644
--- a/app/code/core/Mage/CatalogIndex/Model/Indexer/Tierprice.php
+++ b/app/code/core/Mage/CatalogIndex/Model/Indexer/Tierprice.php
@@ -68,7 +68,7 @@ protected function _construct()
      * @param Mage_Eav_Model_Entity_Attribute_Abstract|null $attribute
      * @return array
      */
-    public function createIndexData(Mage_Catalog_Model_Product $object, Mage_Eav_Model_Entity_Attribute_Abstract $attribute = null)
+    public function createIndexData(Mage_Catalog_Model_Product $object, ?Mage_Eav_Model_Entity_Attribute_Abstract $attribute = null)
     {
         $data = [];
 
diff --git a/app/code/core/Mage/Checkout/Model/Api/Resource.php b/app/code/core/Mage/Checkout/Model/Api/Resource.php
index aebdaf50c69..510c821ae51 100644
--- a/app/code/core/Mage/Checkout/Model/Api/Resource.php
+++ b/app/code/core/Mage/Checkout/Model/Api/Resource.php
@@ -144,7 +144,7 @@ protected function _getStoreIdFromQuote($quoteId)
      * @param array|null $attributes
      * @return $this
      */
-    protected function _updateAttributes($data, $object, $type, array $attributes = null)
+    protected function _updateAttributes($data, $object, $type, ?array $attributes = null)
     {
         foreach ($data as $attribute => $value) {
             if ($this->_isAllowedAttribute($attribute, $type, $attributes)) {
@@ -163,7 +163,7 @@ protected function _updateAttributes($data, $object, $type, array $attributes =
      * @param array|null $attributes
      * @return array
      */
-    protected function _getAttributes($object, $type, array $attributes = null)
+    protected function _getAttributes($object, $type, ?array $attributes = null)
     {
         $result = [];
 
@@ -202,7 +202,7 @@ protected function _getAttributes($object, $type, array $attributes = null)
      * @param array|null $attributes
      * @return bool
      */
-    protected function _isAllowedAttribute($attributeCode, $type, array $attributes = null)
+    protected function _isAllowedAttribute($attributeCode, $type, ?array $attributes = null)
     {
         if (!empty($attributes)
             && !(in_array($attributeCode, $attributes))
diff --git a/app/code/core/Mage/Core/Controller/Varien/Action.php b/app/code/core/Mage/Core/Controller/Varien/Action.php
index d15c76b0522..f2e7ef81ada 100644
--- a/app/code/core/Mage/Core/Controller/Varien/Action.php
+++ b/app/code/core/Mage/Core/Controller/Varien/Action.php
@@ -613,7 +613,7 @@ public function noCookiesAction()
      * @param string|null $module
      * @param array|null $params
      */
-    protected function _forward($action, $controller = null, $module = null, array $params = null)
+    protected function _forward($action, $controller = null, $module = null, ?array $params = null)
     {
         $request = $this->getRequest();
 
diff --git a/app/code/core/Mage/Core/Model/Url/Rewrite.php b/app/code/core/Mage/Core/Model/Url/Rewrite.php
index 8340326a0c3..a9bae5f2912 100644
--- a/app/code/core/Mage/Core/Model/Url/Rewrite.php
+++ b/app/code/core/Mage/Core/Model/Url/Rewrite.php
@@ -207,7 +207,7 @@ public function removeTag($tags)
      * @throws Mage_Core_Model_Store_Exception
      * @deprecated since 1.7.0.2. Refactored and moved to Mage_Core_Controller_Request_Rewrite
      */
-    public function rewrite(Zend_Controller_Request_Http $request = null, Zend_Controller_Response_Http $response = null)
+    public function rewrite(?Zend_Controller_Request_Http $request = null, ?Zend_Controller_Response_Http $response = null)
     {
         if (!Mage::isInstalled()) {
             return false;
diff --git a/app/code/core/Mage/Customer/Block/Address/Renderer/Default.php b/app/code/core/Mage/Customer/Block/Address/Renderer/Default.php
index 7d5ed495c87..768be5478eb 100644
--- a/app/code/core/Mage/Customer/Block/Address/Renderer/Default.php
+++ b/app/code/core/Mage/Customer/Block/Address/Renderer/Default.php
@@ -54,7 +54,7 @@ public function setType(Varien_Object $type)
      * @param Mage_Customer_Model_Address_Abstract|null $address
      * @return string
      */
-    public function getFormat(Mage_Customer_Model_Address_Abstract $address = null)
+    public function getFormat(?Mage_Customer_Model_Address_Abstract $address = null)
     {
         $countryFormat = is_null($address)
             ? false
diff --git a/app/code/core/Mage/Customer/Model/Api/Resource.php b/app/code/core/Mage/Customer/Model/Api/Resource.php
index 1cffa839a89..4c684a1fcf7 100644
--- a/app/code/core/Mage/Customer/Model/Api/Resource.php
+++ b/app/code/core/Mage/Customer/Model/Api/Resource.php
@@ -42,7 +42,7 @@ class Mage_Customer_Model_Api_Resource extends Mage_Api_Model_Resource_Abstract
      * @param array|null $filter
      * @return bool
      */
-    protected function _isAllowedAttribute($attribute, array $filter = null)
+    protected function _isAllowedAttribute($attribute, ?array $filter = null)
     {
         if (!is_null($filter)
             && !(in_array($attribute->getAttributeCode(), $filter)
@@ -62,7 +62,7 @@ protected function _isAllowedAttribute($attribute, array $filter = null)
      * @param array|null $filter
      * @return array
      */
-    public function getAllowedAttributes($entity, array $filter = null)
+    public function getAllowedAttributes($entity, ?array $filter = null)
     {
         $attributes = $entity->getResource()
                         ->loadAllAttributes($entity)
diff --git a/app/code/core/Mage/Dataflow/Model/Convert/Action/Abstract.php b/app/code/core/Mage/Dataflow/Model/Convert/Action/Abstract.php
index e7c61b06a6e..923467a650c 100644
--- a/app/code/core/Mage/Dataflow/Model/Convert/Action/Abstract.php
+++ b/app/code/core/Mage/Dataflow/Model/Convert/Action/Abstract.php
@@ -123,7 +123,7 @@ public function setProfile(Mage_Dataflow_Model_Convert_Profile_Interface $profil
         return $this;
     }
 
-    public function addAction(Mage_Dataflow_Model_Convert_Action_Interface $action = null)
+    public function addAction(?Mage_Dataflow_Model_Convert_Action_Interface $action = null)
     {
         if (is_null($action)) {
             $action = new $this->_actionDefaultClass();
diff --git a/app/code/core/Mage/Dataflow/Model/Convert/Profile/Abstract.php b/app/code/core/Mage/Dataflow/Model/Convert/Profile/Abstract.php
index d6c440a7cf3..cc4d6325ad4 100644
--- a/app/code/core/Mage/Dataflow/Model/Convert/Profile/Abstract.php
+++ b/app/code/core/Mage/Dataflow/Model/Convert/Profile/Abstract.php
@@ -34,7 +34,7 @@ abstract class Mage_Dataflow_Model_Convert_Profile_Abstract implements Mage_Data
 
     protected $_dataflow_profile = null;
 
-    public function addAction(Mage_Dataflow_Model_Convert_Action_Interface $action = null)
+    public function addAction(?Mage_Dataflow_Model_Convert_Action_Interface $action = null)
     {
         if (is_null($action)) {
             $action = new $this->_actionDefaultClass();
diff --git a/app/code/core/Mage/Dataflow/Model/Convert/Profile/Collection.php b/app/code/core/Mage/Dataflow/Model/Convert/Profile/Collection.php
index 491d1ef2383..4e039562d33 100644
--- a/app/code/core/Mage/Dataflow/Model/Convert/Profile/Collection.php
+++ b/app/code/core/Mage/Dataflow/Model/Convert/Profile/Collection.php
@@ -70,7 +70,7 @@ public function getProfile($name)
         return $this->_profiles[$name];
     }
 
-    public function addProfile($name, Mage_Dataflow_Model_Convert_Profile_Interface $profile = null)
+    public function addProfile($name, ?Mage_Dataflow_Model_Convert_Profile_Interface $profile = null)
     {
         if (is_null($profile)) {
             $profile = new $this->_profileDefaultClass();
diff --git a/app/code/core/Mage/Newsletter/Model/Template.php b/app/code/core/Mage/Newsletter/Model/Template.php
index 95525a16751..2471f4701f6 100644
--- a/app/code/core/Mage/Newsletter/Model/Template.php
+++ b/app/code/core/Mage/Newsletter/Model/Template.php
@@ -284,7 +284,7 @@ public function getMail()
      * @return bool
      * @deprecated since 1.4.0.1
      **/
-    public function send($subscriber, array $variables = [], $name = null, Mage_Newsletter_Model_Queue $queue = null)
+    public function send($subscriber, array $variables = [], $name = null, ?Mage_Newsletter_Model_Queue $queue = null)
     {
         if (!$this->isValidForSend()) {
             return false;
diff --git a/app/code/core/Mage/Oauth/Model/Server.php b/app/code/core/Mage/Oauth/Model/Server.php
index 3ca44181a77..1e995726b21 100644
--- a/app/code/core/Mage/Oauth/Model/Server.php
+++ b/app/code/core/Mage/Oauth/Model/Server.php
@@ -658,7 +658,7 @@ public function initiateToken()
      * @return string
      * @throws Zend_Controller_Response_Exception
      */
-    public function reportProblem(Exception $e, Zend_Controller_Response_Http $response = null)
+    public function reportProblem(Exception $e, ?Zend_Controller_Response_Http $response = null)
     {
         $eMsg = $e->getMessage();
 
diff --git a/app/code/core/Mage/Payment/Model/Recurring/Profile.php b/app/code/core/Mage/Payment/Model/Recurring/Profile.php
index 2c1b1f98427..d04e8252e38 100644
--- a/app/code/core/Mage/Payment/Model/Recurring/Profile.php
+++ b/app/code/core/Mage/Payment/Model/Recurring/Profile.php
@@ -302,7 +302,7 @@ public function exportScheduleInfo()
      * @return $this
      * @throws Zend_Date_Exception
      */
-    public function setNearestStartDatetime(Zend_Date $minAllowed = null)
+    public function setNearestStartDatetime(?Zend_Date $minAllowed = null)
     {
         // TODO: implement proper logic with invoking payment method instance
         $date = $minAllowed;
diff --git a/app/code/core/Mage/Paypal/Model/Config.php b/app/code/core/Mage/Paypal/Model/Config.php
index 8c74ac35339..af3cb556d9c 100644
--- a/app/code/core/Mage/Paypal/Model/Config.php
+++ b/app/code/core/Mage/Paypal/Model/Config.php
@@ -1178,7 +1178,7 @@ public function getPaymentMarkImageUrl($localeCode, $orderTotal = null, $pal = n
      * @param Mage_Core_Model_Locale|null $locale
      * @return string
      */
-    public function getPaymentMarkWhatIsPaypalUrl(Mage_Core_Model_Locale $locale = null)
+    public function getPaymentMarkWhatIsPaypalUrl(?Mage_Core_Model_Locale $locale = null)
     {
         $countryCode = 'US';
         if ($locale !== null) {
diff --git a/app/code/core/Mage/Paypal/Model/Info.php b/app/code/core/Mage/Paypal/Model/Info.php
index cd177f1f8fd..17c839d6a0e 100644
--- a/app/code/core/Mage/Paypal/Model/Info.php
+++ b/app/code/core/Mage/Paypal/Model/Info.php
@@ -210,7 +210,7 @@ public function importToPayment($from, Mage_Payment_Model_Info $payment)
      * @param array|null $map
      * @return array|Varien_Object
      */
-    public function &exportFromPayment(Mage_Payment_Model_Info $payment, $to, array $map = null)
+    public function &exportFromPayment(Mage_Payment_Model_Info $payment, $to, ?array $map = null)
     {
         $fullMap = array_merge($this->_paymentMap, $this->_systemMap);
         Varien_Object_Mapper::accumulateByMap(
diff --git a/app/code/core/Mage/Paypal/Model/Ipn.php b/app/code/core/Mage/Paypal/Model/Ipn.php
index e13b11f44ec..665613a9124 100644
--- a/app/code/core/Mage/Paypal/Model/Ipn.php
+++ b/app/code/core/Mage/Paypal/Model/Ipn.php
@@ -89,7 +89,7 @@ public function getRequestData($key = null)
      * @param Zend_Http_Client_Adapter_Interface|null $httpAdapter
      * @throws Mage_Core_Exception
      */
-    public function processIpnRequest(array $request, Zend_Http_Client_Adapter_Interface $httpAdapter = null)
+    public function processIpnRequest(array $request, ?Zend_Http_Client_Adapter_Interface $httpAdapter = null)
     {
         $this->_request   = $request;
         $this->_debugData = ['ipn' => $request];
diff --git a/app/code/core/Mage/Reports/Model/Resource/Event.php b/app/code/core/Mage/Reports/Model/Resource/Event.php
index b5ad2ca8c49..b2a81ecd901 100644
--- a/app/code/core/Mage/Reports/Model/Resource/Event.php
+++ b/app/code/core/Mage/Reports/Model/Resource/Event.php
@@ -112,7 +112,7 @@ public function applyLogToCollection(
      * @return array
      * @throws Mage_Core_Model_Store_Exception
      */
-    public function getCurrentStoreIds(array $predefinedStoreIds = null)
+    public function getCurrentStoreIds(?array $predefinedStoreIds = null)
     {
         $stores = [];
         // get all or specified stores
diff --git a/app/code/core/Mage/Review/Model/Resource/Review/Product/Collection.php b/app/code/core/Mage/Review/Model/Resource/Review/Product/Collection.php
index 8bffc3e9d8d..15df70d30f0 100644
--- a/app/code/core/Mage/Review/Model/Resource/Review/Product/Collection.php
+++ b/app/code/core/Mage/Review/Model/Resource/Review/Product/Collection.php
@@ -131,7 +131,7 @@ public function setStoreFilter($storeId)
      * @param null|Zend_Db_Select $select
      * @return $this
      */
-    protected function _applyStoresFilterToSelect(Zend_Db_Select $select = null)
+    protected function _applyStoresFilterToSelect(?Zend_Db_Select $select = null)
     {
         $adapter = $this->getConnection();
         $storesIds = $this->_storesIds;
diff --git a/app/code/core/Mage/Rule/Model/Resource/Rule/Collection/Abstract.php b/app/code/core/Mage/Rule/Model/Resource/Rule/Collection/Abstract.php
index 5f72ee728bb..e96de3c44ad 100644
--- a/app/code/core/Mage/Rule/Model/Resource/Rule/Collection/Abstract.php
+++ b/app/code/core/Mage/Rule/Model/Resource/Rule/Collection/Abstract.php
@@ -173,7 +173,7 @@ protected function _getAssociatedEntityInfo($entityType)
      * @deprecated after 1.6.2.0
      *
      */
-    public function setEnv(Mage_Rule_Model_Environment $env = null)
+    public function setEnv(?Mage_Rule_Model_Environment $env = null)
     {
         $this->_env = $env;
         return $this;
diff --git a/app/code/core/Mage/Sales/Model/Api/Resource.php b/app/code/core/Mage/Sales/Model/Api/Resource.php
index 79c949c62f1..9e1617c2086 100644
--- a/app/code/core/Mage/Sales/Model/Api/Resource.php
+++ b/app/code/core/Mage/Sales/Model/Api/Resource.php
@@ -48,7 +48,7 @@ class Mage_Sales_Model_Api_Resource extends Mage_Api_Model_Resource_Abstract
      * @param array|null $attributes
      * @return $this
      */
-    protected function _updateAttributes($data, $object, $type, array $attributes = null)
+    protected function _updateAttributes($data, $object, $type, ?array $attributes = null)
     {
         foreach ($data as $attribute => $value) {
             if ($this->_isAllowedAttribute($attribute, $type, $attributes)) {
@@ -67,7 +67,7 @@ protected function _updateAttributes($data, $object, $type, array $attributes =
      * @param array|null $attributes
      * @return array
      */
-    protected function _getAttributes($object, $type, array $attributes = null)
+    protected function _getAttributes($object, $type, ?array $attributes = null)
     {
         $result = [];
 
@@ -104,7 +104,7 @@ protected function _getAttributes($object, $type, array $attributes = null)
      * @param array|null $attributes
      * @return bool
      */
-    protected function _isAllowedAttribute($attributeCode, $type, array $attributes = null)
+    protected function _isAllowedAttribute($attributeCode, $type, ?array $attributes = null)
     {
         if (!empty($attributes)
             && !(in_array($attributeCode, $attributes))
diff --git a/app/code/core/Mage/Sales/Model/Quote.php b/app/code/core/Mage/Sales/Model/Quote.php
index c051774cdb7..aa59600757f 100644
--- a/app/code/core/Mage/Sales/Model/Quote.php
+++ b/app/code/core/Mage/Sales/Model/Quote.php
@@ -458,8 +458,8 @@ public function assignCustomer(Mage_Customer_Model_Customer $customer)
      */
     public function assignCustomerWithAddressChange(
         Mage_Customer_Model_Customer    $customer,
-        Mage_Sales_Model_Quote_Address  $billingAddress = null,
-        Mage_Sales_Model_Quote_Address  $shippingAddress = null
+        ?Mage_Sales_Model_Quote_Address  $billingAddress = null,
+        ?Mage_Sales_Model_Quote_Address  $shippingAddress = null
     ) {
         if ($customer->getId()) {
             $this->setCustomer($customer);
diff --git a/app/code/core/Mage/Sales/Model/Quote/Address.php b/app/code/core/Mage/Sales/Model/Quote/Address.php
index b6147eb0829..beeabfbdb31 100644
--- a/app/code/core/Mage/Sales/Model/Quote/Address.php
+++ b/app/code/core/Mage/Sales/Model/Quote/Address.php
@@ -972,7 +972,7 @@ public function collectShippingRates()
      * @param Mage_Sales_Model_Quote_Item_Abstract|null $item
      * @return bool
      */
-    public function requestShippingRates(Mage_Sales_Model_Quote_Item_Abstract $item = null)
+    public function requestShippingRates(?Mage_Sales_Model_Quote_Item_Abstract $item = null)
     {
         /** @var Mage_Shipping_Model_Rate_Request $request */
         $request = Mage::getModel('shipping/rate_request');
diff --git a/app/code/core/Mage/Shipping/Model/Carrier/Abstract.php b/app/code/core/Mage/Shipping/Model/Carrier/Abstract.php
index 881711361b4..af144e6827d 100644
--- a/app/code/core/Mage/Shipping/Model/Carrier/Abstract.php
+++ b/app/code/core/Mage/Shipping/Model/Carrier/Abstract.php
@@ -170,7 +170,7 @@ public function returnOfShipment($request)
      * @param Varien_Object|null $params
      * @return array
      */
-    public function getContainerTypes(Varien_Object $params = null)
+    public function getContainerTypes(?Varien_Object $params = null)
     {
         return [];
     }
@@ -181,7 +181,7 @@ public function getContainerTypes(Varien_Object $params = null)
      * @param Varien_Object|null $params
      * @return array|bool
      */
-    protected function _getAllowedContainers(Varien_Object $params = null)
+    protected function _getAllowedContainers(?Varien_Object $params = null)
     {
         $containersAll = $this->getContainerTypesAll();
         if (empty($containersAll)) {
@@ -244,7 +244,7 @@ public function getCustomizableContainerTypes()
      * @param Varien_Object|null $params
      * @return array
      */
-    public function getDeliveryConfirmationTypes(Varien_Object $params = null)
+    public function getDeliveryConfirmationTypes(?Varien_Object $params = null)
     {
         return [];
     }
diff --git a/app/code/core/Mage/Usa/Model/Shipping/Carrier/Dhl.php b/app/code/core/Mage/Usa/Model/Shipping/Carrier/Dhl.php
index cb89380b28f..17b72682502 100644
--- a/app/code/core/Mage/Usa/Model/Shipping/Carrier/Dhl.php
+++ b/app/code/core/Mage/Usa/Model/Shipping/Carrier/Dhl.php
@@ -1325,7 +1325,7 @@ protected function _doShipmentRequest(Varien_Object $request)
      * @param Varien_Object|null $params
      * @return array|bool
      */
-    public function getContainerTypes(Varien_Object $params = null)
+    public function getContainerTypes(?Varien_Object $params = null)
     {
         return $this->getCode('shipment_type');
     }
diff --git a/app/code/core/Mage/Usa/Model/Shipping/Carrier/Dhl/International.php b/app/code/core/Mage/Usa/Model/Shipping/Carrier/Dhl/International.php
index 2b2fc2a5bc0..8700e0181ed 100644
--- a/app/code/core/Mage/Usa/Model/Shipping/Carrier/Dhl/International.php
+++ b/app/code/core/Mage/Usa/Model/Shipping/Carrier/Dhl/International.php
@@ -1176,7 +1176,7 @@ protected function _showError()
      * @param Varien_Object|null $params
      * @return array
      */
-    public function getContainerTypes(Varien_Object $params = null)
+    public function getContainerTypes(?Varien_Object $params = null)
     {
         return [
             self::DHL_CONTENT_TYPE_DOC      => Mage::helper('usa')->__('Documents'),
diff --git a/app/code/core/Mage/Usa/Model/Shipping/Carrier/Fedex.php b/app/code/core/Mage/Usa/Model/Shipping/Carrier/Fedex.php
index 76a64f33d3c..ee3bdb4ce14 100644
--- a/app/code/core/Mage/Usa/Model/Shipping/Carrier/Fedex.php
+++ b/app/code/core/Mage/Usa/Model/Shipping/Carrier/Fedex.php
@@ -1550,7 +1550,7 @@ public function rollBack($data)
      * @param Varien_Object|null $params
      * @return array|bool
      */
-    public function getContainerTypes(Varien_Object $params = null)
+    public function getContainerTypes(?Varien_Object $params = null)
     {
         if ($params == null) {
             return $this->_getAllowedContainers($params);
@@ -1607,7 +1607,7 @@ public function getContainerTypesFilter()
      * @param Varien_Object|null $params
      * @return array
      */
-    public function getDeliveryConfirmationTypes(Varien_Object $params = null)
+    public function getDeliveryConfirmationTypes(?Varien_Object $params = null)
     {
         return $this->getCode('delivery_confirmation_types');
     }
diff --git a/app/code/core/Mage/Usa/Model/Shipping/Carrier/Ups.php b/app/code/core/Mage/Usa/Model/Shipping/Carrier/Ups.php
index 102bc94a279..b886a53c52e 100644
--- a/app/code/core/Mage/Usa/Model/Shipping/Carrier/Ups.php
+++ b/app/code/core/Mage/Usa/Model/Shipping/Carrier/Ups.php
@@ -2028,7 +2028,7 @@ protected function _doShipmentRequestXML(Varien_Object $request): Varien_Object
      * @param Varien_Object|null $params
      * @return array|bool
      */
-    public function getContainerTypes(Varien_Object $params = null)
+    public function getContainerTypes(?Varien_Object $params = null)
     {
         if ($params == null) {
             return $this->_getAllowedContainers($params);
@@ -2112,7 +2112,7 @@ public function getContainerTypesFilter()
      * @param Varien_Object|null $params
      * @return array
      */
-    public function getDeliveryConfirmationTypes(Varien_Object $params = null)
+    public function getDeliveryConfirmationTypes(?Varien_Object $params = null)
     {
         $countryRecipient           = $params != null ? $params->getCountryRecipient() : null;
         $deliveryConfirmationTypes  = [];
diff --git a/app/code/core/Mage/Usa/Model/Shipping/Carrier/Usps.php b/app/code/core/Mage/Usa/Model/Shipping/Carrier/Usps.php
index b7c995d0f3e..e4af94befeb 100644
--- a/app/code/core/Mage/Usa/Model/Shipping/Carrier/Usps.php
+++ b/app/code/core/Mage/Usa/Model/Shipping/Carrier/Usps.php
@@ -1804,7 +1804,7 @@ protected function _doShipmentRequest(Varien_Object $request)
      * @param Varien_Object|null $params
      * @return array|bool
      */
-    public function getContainerTypes(Varien_Object $params = null)
+    public function getContainerTypes(?Varien_Object $params = null)
     {
         if (is_null($params)) {
             return $this->_getAllowedContainers();
@@ -1838,7 +1838,7 @@ public function getContainerTypesFilter()
      * @param Varien_Object|null $params
      * @return array
      */
-    public function getDeliveryConfirmationTypes(Varien_Object $params = null)
+    public function getDeliveryConfirmationTypes(?Varien_Object $params = null)
     {
         if ($params == null) {
             return [];
diff --git a/composer.json b/composer.json
index 663b91a6660..a63c329cfb3 100644
--- a/composer.json
+++ b/composer.json
@@ -7,7 +7,7 @@
     ],
     "type": "magento-source",
     "require": {
-        "php": ">=7.4 <8.4",
+        "php": ">=7.4 <8.5",
         "ext-ctype": "*",
         "ext-curl": "*",
         "ext-dom": "*",
diff --git a/composer.lock b/composer.lock
index 43057d1cae4..1a60e226911 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "76dfca273981ae0e9388059e1108e257",
+    "content-hash": "40e9d3cfc444bb72b7cf7754c735f694",
     "packages": [
         {
             "name": "colinmollenhour/cache-backend-redis",
@@ -405,12 +405,12 @@
             "version": "v5.2.13",
             "source": {
                 "type": "git",
-                "url": "https://github.com/justinrainbow/json-schema.git",
+                "url": "https://github.com/jsonrainbow/json-schema.git",
                 "reference": "fbbe7e5d79f618997bc3332a6f49246036c45793"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/justinrainbow/json-schema/zipball/fbbe7e5d79f618997bc3332a6f49246036c45793",
+                "url": "https://api.github.com/repos/jsonrainbow/json-schema/zipball/fbbe7e5d79f618997bc3332a6f49246036c45793",
                 "reference": "fbbe7e5d79f618997bc3332a6f49246036c45793",
                 "shasum": ""
             },
@@ -6392,7 +6392,7 @@
     "prefer-stable": true,
     "prefer-lowest": false,
     "platform": {
-        "php": ">=7.4 <8.4",
+        "php": ">=7.4 <8.5",
         "ext-ctype": "*",
         "ext-curl": "*",
         "ext-dom": "*",
diff --git a/lib/Varien/Convert/Profile/Abstract.php b/lib/Varien/Convert/Profile/Abstract.php
index c18806d4990..dfd2d76a856 100644
--- a/lib/Varien/Convert/Profile/Abstract.php
+++ b/lib/Varien/Convert/Profile/Abstract.php
@@ -29,7 +29,7 @@ abstract class Varien_Convert_Profile_Abstract
     protected $_actionDefaultClass = 'Varien_Convert_Action';
     protected $_containerCollectionDefaultClass = 'Varien_Convert_Container_Collection';
 
-    public function addAction(Varien_Convert_Action_Interface $action = null)
+    public function addAction(?Varien_Convert_Action_Interface $action = null)
     {
         if (is_null($action)) {
             $action = new $this->_actionDefaultClass();
diff --git a/lib/Varien/Convert/Profile/Collection.php b/lib/Varien/Convert/Profile/Collection.php
index 7ac0fb539e5..54134b076b1 100644
--- a/lib/Varien/Convert/Profile/Collection.php
+++ b/lib/Varien/Convert/Profile/Collection.php
@@ -64,7 +64,7 @@ public function getProfile($name)
         return $this->_profiles[$name];
     }
 
-    public function addProfile($name, Varien_Convert_Profile_Abstract $profile = null)
+    public function addProfile($name, ?Varien_Convert_Profile_Abstract $profile = null)
     {
         if (is_null($profile)) {
             $profile = new $this->_profileDefaultClass();
diff --git a/lib/Varien/Db/Statement/Pdo/Mysql.php b/lib/Varien/Db/Statement/Pdo/Mysql.php
index 02c5432a5d5..b23cb8435fa 100644
--- a/lib/Varien/Db/Statement/Pdo/Mysql.php
+++ b/lib/Varien/Db/Statement/Pdo/Mysql.php
@@ -79,7 +79,7 @@ public function _executeWithBinding(array $params)
      * @return bool
      * @throws Zend_Db_Statement_Exception
      */
-    public function _execute(array $params = null)
+    public function _execute(?array $params = null)
     {
         $specialExecute = false;
         if ($params) {