null variable declaration deprecation fix

.github/workflows/php.yml

@@ -11,9 +11,9 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php-versions: ['7.2', '7.3', '7.4', '8.0','8.1','8.2','8.3']
+        php-versions: ['7.2', '7.3', '7.4', '8.0','8.1','8.2','8.3','8.4']
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
 
     - name: Setup PHP
       uses: shivammathur/setup-php@v2
@@ -25,7 +25,7 @@ jobs:
 
     - name: Cache Composer packages
       id: composer-cache
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       with:
         path: vendor
         key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}

composer.json

@@ -12,10 +12,11 @@
     },
     "require-dev": {
         "monolog/monolog"           : "~1.0",
-        "phpspec/phpspec"           : "~6.2||7.*",
+        "phpspec/phpspec"           : "~6.2||7.*||dev-main",
         "phpunit/phpunit"           : "^8.5",
         "symfony/yaml"              : ">=4.4"
     },
+    "prefer-stable": true,
     "config": {
         "bin-dir": "bin"
     },

phpunit.xml.dist

@@ -15,8 +15,8 @@
 
     <php>
         <!-- For integration tests -->
-        <env name="CONSUMER_KEY" value=""/>
-        <env name="CONSUMER_SECRET" value=""/>
+        <env name="CONSUMER_KEY" value="test_jhcm1kuiowcs2s9dj03vryr4v8yf4f"/>
+        <env name="CONSUMER_SECRET" value="uczqtwmhh2dj1m2vkulspssqisqc2qzjo8v23auqssux4opvaf"/>
     </php>
 
     <testsuites>

src/Exception/Request.php

@@ -10,10 +10,10 @@ class Request extends Runtime
     private $result;
 
     /**
-     * @param \Exception $previous
-     * @param ResultObjectInterface $result
+     * @param \Exception|null $previous
+     * @param ResultObjectInterface|null $result
      */
-    public function __construct(\Exception $previous = null, ResultObjectInterface $result = null)
+    public function __construct(?\Exception $previous = null, ?ResultObjectInterface $result = null)
     {
         $this->message .= ' Response data: ' . serialize($result);
         parent::__construct($this->message, $this->code, $previous);

src/Method/Payment/Create.php

@@ -205,7 +205,7 @@ private function getCardHolderInfoConstraints(): object
     private function buildElement(
         string $typeValue,
         bool $isRequired = false,
-        array $length = null,
+        ?array $length = null,
         $args = null // TODO can it be null?
     ): object
     {