diff --git a/.github/workflows/bc_check.yaml b/.github/workflows/bc_check.yaml
index 146c787..131ddb5 100644
--- a/.github/workflows/bc_check.yaml
+++ b/.github/workflows/bc_check.yaml
@@ -17,7 +17,7 @@ jobs:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: 7.4
+          php-version: '8.0'
       - name: Install Checker
         run: composer require --dev roave/backward-compatibility-check
       - name: Check for BC breaks
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 5e9b94a..f464f6a 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -13,7 +13,7 @@ jobs:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: '7.4'
+          php-version: '8.0'
       - name: Checkout Code
         uses: actions/checkout@v2
       - name: Install Dependencies
@@ -25,12 +25,12 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        symfonyVersion: [ ^4.4, ^5.0 ]
+        symfonyVersion: [^6.0]
     steps:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: '7.4'
+          php-version: '8.0'
       - name: Checkout Code
         uses: actions/checkout@v2
       - name: Install Dependencies
@@ -44,12 +44,12 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        symfonyVersion: [^4.4, ^5.0]
+        symfonyVersion: [^6.0]
     steps:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: '7.4'
+          php-version: '8.0'
       - name: Checkout Code
         uses: actions/checkout@v2
       - name: Install Dependencies
@@ -65,7 +65,7 @@ jobs:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: '7.4'
+          php-version: '8.0'
       - name: Checkout Code
         uses: actions/checkout@v2
       - name: Install Dependencies
diff --git a/.php_cs.dist b/.php-cs-fixer.dist.php
similarity index 95%
rename from .php_cs.dist
rename to .php-cs-fixer.dist.php
index 0bfb0e3..461197e 100644
--- a/.php_cs.dist
+++ b/.php-cs-fixer.dist.php
@@ -1,6 +1,6 @@
 <?php
 
-return PhpCsFixer\Config::create()
+return (new \PhpCsFixer\Config())
     ->setRules([
         '@PSR2' => true,
         'array_syntax' => ['syntax' => 'short'],
@@ -10,7 +10,7 @@
         ],
         'cast_spaces' => true,
         'class_attributes_separation' => [
-            'elements' => ['method', 'property'],
+            'elements' => ['method' => 'one', 'property' => 'one'],
         ],
         'combine_consecutive_unsets' => true,
         'compact_nullable_typehint' => true,
@@ -70,7 +70,7 @@
         'single_quote' => true,
         'standardize_not_equals' => true,
         'ternary_operator_spaces' => true,
-        'trailing_comma_in_multiline_array' => true,
+        'trailing_comma_in_multiline' => true,
         'unary_operator_spaces' => true,
         'visibility_required' => [
             'elements' => ['property', 'method', 'const'],
diff --git a/composer.json b/composer.json
index 8d96834..8ce7bbc 100644
--- a/composer.json
+++ b/composer.json
@@ -5,10 +5,10 @@
   "minimum-stability": "stable",
   "license": "MIT",
   "require": {
-    "symfony/framework-bundle": "^4.4 | ^5.0",
+    "symfony/framework-bundle": "^6.0",
     "rikudou/psr6-dynamo-db": "^2.0",
-    "php": "^7.2 | ^8.0",
-    "symfony/cache": "^4.4 | ^5.0",
+    "php": "^8.0",
+    "symfony/cache": "^6.0",
     "ext-json": "*"
   },
   "autoload": {
@@ -17,9 +17,9 @@
     }
   },
   "require-dev": {
-    "friendsofphp/php-cs-fixer": "^2.16",
-    "phpstan/phpstan": "^0.12.44",
-    "phpunit/phpunit": "^9.3"
+    "friendsofphp/php-cs-fixer": "^3.0",
+    "phpstan/phpstan": "^1.5",
+    "phpunit/phpunit": "^9.5"
   },
   "autoload-dev": {
     "psr-4": {
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index c1aa00f..a473a4c 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -1,5 +1,4 @@
 parameters:
-  excludes_analyse:
-    - src/DependencyInjection/Configuration.php
-  ignoreErrors:
-    - '#Return type .*? of method .*?DynamoDbCacheAdapter::getItems.*? should be compatible .*#'
+  excludePaths:
+    analyse:
+      - src/DependencyInjection/Configuration.php
diff --git a/src/Cache/DynamoDbCacheAdapter.php b/src/Cache/DynamoDbCacheAdapter.php
index 73f4ff0..7076580 100644
--- a/src/Cache/DynamoDbCacheAdapter.php
+++ b/src/Cache/DynamoDbCacheAdapter.php
@@ -16,24 +16,14 @@ final class DynamoDbCacheAdapter implements AdapterInterface, CacheInterface
 {
     use CacheTrait;
 
-    /**
-     * @var DynamoDbCache
-     */
-    private $cache;
-
-    /**
-     * @var SymfonyCacheItemConverter
-     */
-    private $converter;
-
     /**
      * @param DynamoDbCache             $cache
      * @param SymfonyCacheItemConverter $converter
      */
-    public function __construct(DynamoDbCache $cache, SymfonyCacheItemConverter $converter)
-    {
-        $this->cache = $cache;
-        $this->converter = $converter;
+    public function __construct(
+        private DynamoDbCache $cache,
+        private SymfonyCacheItemConverter $converter
+    ) {
     }
 
     /**
@@ -43,7 +33,7 @@ public function __construct(DynamoDbCache $cache, SymfonyCacheItemConverter $con
      *
      * @return CacheItem
      */
-    public function getItem($key)
+    public function getItem(mixed $key): CacheItem
     {
         return $this->converter->convertToCacheItem($this->cache->getItem($key));
     }
@@ -55,7 +45,7 @@ public function getItem($key)
      *
      * @return CacheItem[]
      */
-    public function getItems(array $keys = [])
+    public function getItems(array $keys = []): iterable
     {
         return array_map(function (DynamoCacheItem $item) {
             return $this->converter->convertToCacheItem($item);
@@ -67,7 +57,7 @@ public function getItems(array $keys = [])
      *
      * @return bool
      */
-    public function clear(string $prefix = '')
+    public function clear(string $prefix = ''): bool
     {
         return $this->cache->clear();
     }
@@ -79,7 +69,7 @@ public function clear(string $prefix = '')
      *
      * @return bool
      */
-    public function hasItem($key)
+    public function hasItem(string $key): bool
     {
         return $this->cache->hasItem($key);
     }
@@ -91,7 +81,7 @@ public function hasItem($key)
      *
      * @return bool
      */
-    public function deleteItem($key)
+    public function deleteItem(string $key): bool
     {
         return $this->cache->deleteItem($key);
     }
@@ -103,7 +93,7 @@ public function deleteItem($key)
      *
      * @return bool
      */
-    public function deleteItems(array $keys)
+    public function deleteItems(array $keys): bool
     {
         return $this->cache->deleteItems($keys);
     }
@@ -115,7 +105,7 @@ public function deleteItems(array $keys)
      *
      * @return bool
      */
-    public function save(CacheItemInterface $item)
+    public function save(CacheItemInterface $item): bool
     {
         return $this->cache->save($item);
     }
@@ -127,7 +117,7 @@ public function save(CacheItemInterface $item)
      *
      * @return bool
      */
-    public function saveDeferred(CacheItemInterface $item)
+    public function saveDeferred(CacheItemInterface $item): bool
     {
         return $this->cache->saveDeferred($item);
     }
@@ -137,7 +127,7 @@ public function saveDeferred(CacheItemInterface $item)
      *
      * @return bool
      */
-    public function commit()
+    public function commit(): bool
     {
         return $this->cache->commit();
     }
diff --git a/src/Converter/SymfonyCacheItemConverter.php b/src/Converter/SymfonyCacheItemConverter.php
index f81df68..bb9cc24 100644
--- a/src/Converter/SymfonyCacheItemConverter.php
+++ b/src/Converter/SymfonyCacheItemConverter.php
@@ -14,20 +14,10 @@
 
 final class SymfonyCacheItemConverter implements CacheItemConverterInterface
 {
-    /**
-     * @var ClockInterface
-     */
-    private $clock;
-
-    /**
-     * @var CacheItemEncoderInterface
-     */
-    private $encoder;
-
-    public function __construct(ClockInterface $clock, CacheItemEncoderInterface $encoder)
-    {
-        $this->clock = $clock;
-        $this->encoder = $encoder;
+    public function __construct(
+        private ClockInterface $clock,
+        private CacheItemEncoderInterface $encoder,
+    ) {
     }
 
     public function supports(CacheItemInterface $cacheItem): bool
@@ -43,6 +33,8 @@ public function convert(CacheItemInterface $cacheItem): DynamoCacheItem
             $reflectionExpiry = new ReflectionProperty(CacheItem::class, 'expiry');
             $reflectionExpiry->setAccessible(true);
             $value = $reflectionExpiry->getValue($cacheItem);
+            assert(is_scalar($value) || $value === null);
+
             if ($value === null) {
                 $expiry = null;
             } else {
@@ -85,7 +77,7 @@ public function convertToCacheItem(DynamoCacheItem $dynamoCacheItem): CacheItem
         $valueReflection->setValue($item, $dynamoCacheItem->get());
         $expiryReflection->setValue(
             $item,
-            $expiry ? $expiry->getTimestamp() : null
+            $expiry?->getTimestamp()
         );
 
         return $item;
diff --git a/src/DependencyInjection/RikudouDynamoDbCacheExtension.php b/src/DependencyInjection/RikudouDynamoDbCacheExtension.php
index c170f5f..6244360 100644
--- a/src/DependencyInjection/RikudouDynamoDbCacheExtension.php
+++ b/src/DependencyInjection/RikudouDynamoDbCacheExtension.php
@@ -44,7 +44,10 @@ private function createDynamoClient(ContainerBuilder $container, array $configs)
     {
         if ($configs['client_service']) {
             $client = $configs['client_service'];
+            assert(is_string($client));
         } else {
+            assert(is_array($configs['client_config']));
+
             $service = new Definition(DynamoDbClient::class);
             $service->addArgument([
                 'region' => $configs['client_config']['region'],
@@ -77,6 +80,8 @@ private function createCacheClient(ContainerBuilder $container, array $configs,
      */
     private function createDefaultEncoder(ContainerBuilder $container, array $configs): void
     {
+        assert(is_array($configs['encoder']));
+
         $container->removeDefinition('rikudou.dynamo_cache.encoder.default');
         $container->setAlias('rikudou.dynamo_cache.encoder.default', $configs['encoder']['service']);
     }
@@ -87,11 +92,19 @@ private function createDefaultEncoder(ContainerBuilder $container, array $config
      */
     private function createParameters(ContainerBuilder $container, array $configs): void
     {
+        assert(
+            is_array($configs['replace_default_adapter'])
+            || is_scalar($configs['replace_default_adapter'])
+            || $configs['replace_default_adapter'] === null
+        );
+
         $container->setParameter(
             'rikudou.dynamo_cache.internal.replace_adapter',
             $configs['replace_default_adapter']
         );
 
+        assert(is_array($configs['encoder']));
+
         $container->setParameter(
             'rikudou.dynamo_cache.json_encoder.encode_flags',
             $configs['encoder']['json_options']['encode_flags']
@@ -112,6 +125,8 @@ private function createParameters(ContainerBuilder $container, array $configs):
      */
     private function createSessionHandler(ContainerBuilder $container, array $configs): void
     {
+        assert(is_array($configs['session']));
+
         $definition = $container->getDefinition('rikudou.dynamo_cache.session');
         $definition->setArgument('$ttl', $configs['session']['ttl']);
         $definition->setArgument('$prefix', $configs['session']['prefix']);
diff --git a/src/Helper/DynamoDbCacheAdapterDecorator.php b/src/Helper/DynamoDbCacheAdapterDecorator.php
index e2ddbd6..4827dd8 100644
--- a/src/Helper/DynamoDbCacheAdapterDecorator.php
+++ b/src/Helper/DynamoDbCacheAdapterDecorator.php
@@ -10,113 +10,78 @@
 
 trait DynamoDbCacheAdapterDecorator
 {
-    private $originalAdapter;
-
-    public function __construct(DynamoDbCacheAdapter $originalAdapter)
-    {
-        $this->originalAdapter = $originalAdapter;
+    public function __construct(
+        private DynamoDbCacheAdapter $originalAdapter
+    ) {
     }
 
     /**
-     * @param $key
-     *
      * @throws InvalidArgumentException
-     *
-     * @return CacheItem
      */
-    public function getItem($key)
+    public function getItem(mixed $key): CacheItem
     {
         return $this->originalAdapter->getItem($key);
     }
 
     /**
-     * @param array $keys
-     *
      * @throws InvalidArgumentException
      *
-     * @return CacheItem[]
+     * @return iterable<CacheItem>
      */
-    public function getItems(array $keys = [])
+    public function getItems(array $keys = []): iterable
     {
         return $this->originalAdapter->getItems($keys);
     }
 
-    /**
-     * @param string $prefix
-     *
-     * @return bool
-     */
-    public function clear(string $prefix = '')
+    public function clear(string $prefix = ''): bool
     {
         return $this->originalAdapter->clear($prefix);
     }
 
     /**
-     * @param $key
-     *
      * @throws InvalidArgumentException
-     *
-     * @return bool
      */
-    public function hasItem($key)
+    public function hasItem(string $key): bool
     {
         return $this->originalAdapter->hasItem($key);
     }
 
     /**
-     * @param $key
-     *
      * @throws InvalidArgumentException
-     *
-     * @return bool
      */
-    public function deleteItem($key)
+    public function deleteItem(string $key): bool
     {
         return $this->originalAdapter->deleteItem($key);
     }
 
     /**
-     * @param array $keys
-     *
      * @throws InvalidArgumentException
-     *
-     * @return bool
      */
-    public function deleteItems(array $keys)
+    public function deleteItems(array $keys): bool
     {
         return $this->originalAdapter->deleteItems($keys);
     }
 
     /**
-     * @param CacheItemInterface $item
-     *
      * @throws InvalidArgumentException
-     *
-     * @return bool
      */
-    public function save(CacheItemInterface $item)
+    public function save(CacheItemInterface $item): bool
     {
         return $this->originalAdapter->save($item);
     }
 
     /**
-     * @param CacheItemInterface $item
-     *
      * @throws InvalidArgumentException
-     *
-     * @return bool
      */
-    public function saveDeferred(CacheItemInterface $item)
+    public function saveDeferred(CacheItemInterface $item): bool
     {
         return $this->originalAdapter->saveDeferred($item);
     }
 
     /**
      * @throws InvalidArgumentException
-     *
-     * @return bool
      */
-    public function commit()
+    public function commit(): bool
     {
         return $this->originalAdapter->commit();
     }
diff --git a/src/Session/DynamoDbSessionHandler.php b/src/Session/DynamoDbSessionHandler.php
index 4999ed3..e654cb5 100644
--- a/src/Session/DynamoDbSessionHandler.php
+++ b/src/Session/DynamoDbSessionHandler.php
@@ -9,28 +9,16 @@
 
 final class DynamoDbSessionHandler extends AbstractSessionHandler
 {
-    /**
-     * @var DynamoDbCacheAdapter
-     */
-    private $cache;
-
-    /**
-     * @var string
-     */
-    private $prefix;
-
     /**
      * @var int
      */
-    private $ttl;
+    private int $ttl;
 
     public function __construct(
-        DynamoDbCacheAdapter $cache,
-        string $prefix,
+        private DynamoDbCacheAdapter $cache,
+        private string $prefix,
         ?int $ttl
     ) {
-        $this->cache = $cache;
-        $this->prefix = $prefix;
         $this->ttl = $ttl ?? (int) ini_get('session.gc_maxlifetime');
     }
 
@@ -39,42 +27,34 @@ public function close(): bool
         return true;
     }
 
-    public function gc($maxlifetime): bool
+    public function gc(int $max_lifetime): int|false
     {
-        return true;
+        return 0;
     }
 
     /**
-     * @param string $key
-     * @param string $val
-     *
      * @throws InvalidArgumentException
-     *
-     * @return bool
      */
-    public function updateTimestamp($key, $val): bool
+    public function updateTimestamp(string $id, string $data): bool
     {
-        $item = $this->getCacheItem($key);
+        $item = $this->getCacheItem($id);
         $item->expiresAfter($this->ttl);
 
         return $this->cache->save($item);
     }
 
-    /**
-     * @param string $sessionId
-     */
-    protected function doRead($sessionId): string
+    protected function doRead(string $sessionId): string
     {
-        return (string) $this->getCacheItem($sessionId)->get();
+        $result = $this->getCacheItem($sessionId)->get();
+        assert(is_scalar($result) || $result === null);
+
+        return (string) $result;
     }
 
     /**
-     * @param string $sessionId
-     * @param string $data
-     *
      * @throws InvalidArgumentException
      */
-    protected function doWrite($sessionId, $data): bool
+    protected function doWrite(string $sessionId, string $data): bool
     {
         $item = $this->getCacheItem($sessionId);
         $item->set($data);
@@ -84,11 +64,9 @@ protected function doWrite($sessionId, $data): bool
     }
 
     /**
-     * @param string $sessionId
-     *
      * @throws InvalidArgumentException
      */
-    protected function doDestroy($sessionId): bool
+    protected function doDestroy(string $sessionId): bool
     {
         return $this->cache->deleteItem($this->getCacheKey($sessionId));
     }
@@ -98,6 +76,9 @@ private function getCacheKey(string $sessionId): string
         return $this->prefix . $sessionId;
     }
 
+    /**
+     * @throws InvalidArgumentException
+     */
     private function getCacheItem(string $sessionId): CacheItem
     {
         return $this->cache->getItem($this->getCacheKey($sessionId));
diff --git a/tests/Helper/DynamoDbCacheAdapterDecoratorTest.php b/tests/Helper/DynamoDbCacheAdapterDecoratorTest.php
index e6aed58..6abf4dc 100644
--- a/tests/Helper/DynamoDbCacheAdapterDecoratorTest.php
+++ b/tests/Helper/DynamoDbCacheAdapterDecoratorTest.php
@@ -17,15 +17,9 @@
 
 class DynamoDbCacheAdapterDecoratorTest extends AbstractDynamoDbTest
 {
-    /**
-     * @var DynamoDbCacheAdapter
-     */
-    private $originalInstance;
+    private DynamoDbCacheAdapter $originalInstance;
 
-    /**
-     * @var AdapterInterface|CacheInterface
-     */
-    private $instance;
+    private AdapterInterface|CacheInterface $instance;
 
     protected function setUp(): void
     {
diff --git a/tests/Session/DynamoDbSessionHandlerTest.php b/tests/Session/DynamoDbSessionHandlerTest.php
index 78c4dcb..bfc993e 100644
--- a/tests/Session/DynamoDbSessionHandlerTest.php
+++ b/tests/Session/DynamoDbSessionHandlerTest.php
@@ -68,7 +68,7 @@ public function testClose()
 
     public function testGc()
     {
-        self::assertTrue($this->instance->gc(1));
+        self::assertEquals(0, $this->instance->gc(1));
     }
 
     public function testDoRead()