Fix simple liniting issues

Author: gin0115

.github/workflows/unit-tests.yml

@@ -34,8 +34,12 @@ jobs:
         uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php }}
+          extensions: ${{ matrix.php != '8.1' && 'mbstring' || '' }}
           tools: composer
 
+      - name: Show PHP version
+        run: php -v
+
       - name: Validate composer.json and composer.lock
         run: composer validate --strict