diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f0c9ceb..b97358b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -17,7 +17,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest] # windows-latest, macos-latest
-        php: ['7.2', '7.3', '7.4', '8.0', '8.1', '8.2']
+        php: ['7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
         include:
           - php: 7.2
             phpunit: 7
@@ -31,6 +31,10 @@ jobs:
             phpunit: 9
           - php: 8.2
             phpunit: 9
+          - php: 8.3
+            phpunit: 9
+          - php: 8.4
+            phpunit: 9            
     steps:
     - name: Checkout
       uses: actions/checkout@v3
diff --git a/composer.json b/composer.json
index 9e37ee8..96ec814 100644
--- a/composer.json
+++ b/composer.json
@@ -23,7 +23,7 @@
   },
   "require-dev": {
     "squizlabs/php_codesniffer": "^3.5",
-    "phan/phan": "5.4.2",
+    "phan/phan": "5.4.5",
     "phpunit/phpunit": "^7.5 || ^8.5 || ^9.5"
   },
   "autoload": {
diff --git a/composer.lock b/composer.lock
index efb6251..ca0a4a1 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": "9fdb3ec1706ae57fb5bdfd790d73983f",
+    "content-hash": "d774ca521a28aa59304826a76f1a1b2e",
     "packages": [
         {
             "name": "apimatic/core-interfaces",
@@ -806,16 +806,16 @@
         },
         {
             "name": "phan/phan",
-            "version": "5.4.2",
+            "version": "5.4.5",
             "source": {
                 "type": "git",
                 "url": "https://github.com/phan/phan.git",
-                "reference": "4f2870ed6fea320f62f3c3c63f3274d357a7980e"
+                "reference": "2b15302175931a0629a85c57d0c1f91d68b26a4d"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/phan/phan/zipball/4f2870ed6fea320f62f3c3c63f3274d357a7980e",
-                "reference": "4f2870ed6fea320f62f3c3c63f3274d357a7980e",
+                "url": "https://api.github.com/repos/phan/phan/zipball/2b15302175931a0629a85c57d0c1f91d68b26a4d",
+                "reference": "2b15302175931a0629a85c57d0c1f91d68b26a4d",
                 "shasum": ""
             },
             "require": {
@@ -829,7 +829,7 @@
                 "netresearch/jsonmapper": "^1.6.0|^2.0|^3.0|^4.0",
                 "php": "^7.2.0|^8.0.0",
                 "sabre/event": "^5.1.3",
-                "symfony/console": "^3.2|^4.0|^5.0|^6.0",
+                "symfony/console": "^3.2|^4.0|^5.0|^6.0|^7.0",
                 "symfony/polyfill-mbstring": "^1.11.0",
                 "symfony/polyfill-php80": "^1.20.0",
                 "tysonandre/var_representation_polyfill": "^0.0.2|^0.1.0"
@@ -875,13 +875,14 @@
             "keywords": [
                 "analyzer",
                 "php",
-                "static"
+                "static",
+                "static analysis"
             ],
             "support": {
                 "issues": "https://github.com/phan/phan/issues",
-                "source": "https://github.com/phan/phan/tree/5.4.2"
+                "source": "https://github.com/phan/phan/tree/5.4.5"
             },
-            "time": "2023-03-03T17:20:24+00:00"
+            "time": "2024-08-13T21:41:35+00:00"
         },
         {
             "name": "phar-io/manifest",
@@ -3708,7 +3709,7 @@
     ],
     "aliases": [],
     "minimum-stability": "stable",
-    "stability-flags": [],
+    "stability-flags": {},
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {
@@ -3718,6 +3719,6 @@
         "ext-dom": "*",
         "ext-libxml": "*"
     },
-    "platform-dev": [],
-    "plugin-api-version": "2.0.0"
+    "platform-dev": {},
+    "plugin-api-version": "2.6.0"
 }
diff --git a/src/Client.php b/src/Client.php
index 77c8dfe..dfb18ba 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -22,14 +22,14 @@ class Client
 {
     private static $converter;
     private static $jsonHelper;
-    public static function getConverter(Client $client = null): ConverterInterface
+    public static function getConverter(?Client $client = null): ConverterInterface
     {
         if (isset($client)) {
             return $client->localConverter;
         }
         return self::$converter;
     }
-    public static function getJsonHelper(Client $client = null): JsonHelper
+    public static function getJsonHelper(?Client $client = null): JsonHelper
     {
         if (isset($client)) {
             return $client->localJsonHelper;
diff --git a/src/Types/Sdk/CoreCallback.php b/src/Types/Sdk/CoreCallback.php
index 7731e1a..166dbec 100644
--- a/src/Types/Sdk/CoreCallback.php
+++ b/src/Types/Sdk/CoreCallback.php
@@ -27,7 +27,7 @@ class CoreCallback
      * @param callable|null $onBeforeRequest Called before an API call
      * @param callable|null $onAfterRequest  Called after an API call
      */
-    public function __construct(callable $onBeforeRequest = null, callable $onAfterRequest = null)
+    public function __construct(?callable $onBeforeRequest = null, ?callable $onAfterRequest = null)
     {
         $this->onBeforeRequest = $onBeforeRequest;
         $this->onAfterRequest = $onAfterRequest;
diff --git a/src/Utils/XmlDeserializer.php b/src/Utils/XmlDeserializer.php
index 1e29f12..c67fc7a 100644
--- a/src/Utils/XmlDeserializer.php
+++ b/src/Utils/XmlDeserializer.php
@@ -22,7 +22,7 @@ class XmlDeserializer
     /**
      * @param int|null $loadOptions  A bit field of LIBXML_* constants
      */
-    public function __construct(int $loadOptions = null)
+    public function __construct(?int $loadOptions = null)
     {
         $this->dom = new DOMDocument();
         $this->loadOptions = $loadOptions ?? (LIBXML_NONET | LIBXML_NOBLANKS);
@@ -81,7 +81,7 @@ public function fromElementToArray(
         \DOMNode $parent,
         string $itemName,
         string $clazz,
-        string $wrappingElementName = null
+        ?string $wrappingElementName = null
     ) {
         if ($wrappingElementName === null) {
             $elements = static::getChildNodesByTagName($parent, $itemName);
diff --git a/src/Utils/XmlSerializer.php b/src/Utils/XmlSerializer.php
index 0162abe..170d936 100644
--- a/src/Utils/XmlSerializer.php
+++ b/src/Utils/XmlSerializer.php
@@ -67,7 +67,7 @@ public function addArrayAsSubelement(
         \DOMNode $root,
         string $itemName,
         $items,
-        string $wrappingElementName = null
+        ?string $wrappingElementName = null
     ): void {
         if ($items === null) {
             return;
@@ -102,7 +102,7 @@ public function addAsSubelement(\DOMNode $root, string $name, $value): ?\DOMElem
         return $element;
     }
 
-    public function createElement(string $name, string $value = null): \DOMElement
+    public function createElement(string $name, ?string $value = null): \DOMElement
     {
         return $value === null ? $this->dom->createElement($name) : $this->dom->createElement($name, $value);
     }
diff --git a/tests/LoggerTest.php b/tests/LoggerTest.php
index 89beb5d..8943708 100644
--- a/tests/LoggerTest.php
+++ b/tests/LoggerTest.php
@@ -81,7 +81,7 @@ public function testConsoleLoggerFailure()
 
     private function logAndGetEntry(
         string $level,
-        LoggerInterface $logger = null,
+        ?LoggerInterface $logger = null,
         string $message = 'someMessage',
         array $context = []
     ): LogEntry {