diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index de513a56..6e0cd3c1 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -35,7 +35,7 @@ jobs:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: "8.2"
+          php-version: "8.3"
       - name: Run Script
         run: |
           composer global require friendsofphp/php-cs-fixer
@@ -49,9 +49,9 @@ jobs:
     - name: Install PHP
       uses: shivammathur/setup-php@v2
       with:
-        php-version: '8.2'
+        php-version: '8.3'
     - name: Run Script
       run: |
         composer install
-        composer global require phpstan/phpstan
+        composer global require phpstan/phpstan:~1.10.0
         ~/.composer/vendor/bin/phpstan analyse
diff --git a/src/JWT.php b/src/JWT.php
index 9100bf0f..dd9292a4 100644
--- a/src/JWT.php
+++ b/src/JWT.php
@@ -204,7 +204,7 @@ public static function encode(
         ?array $head = null
     ): string {
         $header = ['typ' => 'JWT'];
-        if (isset($head) && \is_array($head)) {
+        if (isset($head)) {
             $header = \array_merge($header, $head);
         }
         $header['alg'] = $alg;
@@ -387,12 +387,7 @@ public static function jsonDecode(string $input)
      */
     public static function jsonEncode(array $input): string
     {
-        if (PHP_VERSION_ID >= 50400) {
-            $json = \json_encode($input, \JSON_UNESCAPED_SLASHES);
-        } else {
-            // PHP 5.3 only
-            $json = \json_encode($input);
-        }
+        $json = \json_encode($input, \JSON_UNESCAPED_SLASHES);
         if ($errno = \json_last_error()) {
             self::handleJsonError($errno);
         } elseif ($json === 'null') {