diff --git a/Action/Api/CaptureTransactionAction.php b/Action/Api/CaptureTransactionAction.php
index fd18e96..99ab857 100644
--- a/Action/Api/CaptureTransactionAction.php
+++ b/Action/Api/CaptureTransactionAction.php
@@ -12,7 +12,7 @@
 
 class CaptureTransactionAction extends BaseApiAwareAction
 {
-    public function execute($request)
+    public function execute($request): void
     {
         RequestNotSupportedException::assertSupports($this, $request);
         $model = ArrayObject::ensureArrayObject($request->getModel());
diff --git a/Action/AuthorizeAction.php b/Action/AuthorizeAction.php
index 52ee44a..5f0627e 100644
--- a/Action/AuthorizeAction.php
+++ b/Action/AuthorizeAction.php
@@ -18,7 +18,7 @@ class AuthorizeAction implements ActionInterface, GatewayAwareInterface
      *
      * @param Authorize $request
      */
-    public function execute($request)
+    public function execute($request): void
     {
         RequestNotSupportedException::assertSupports($this, $request);
 
@@ -30,7 +30,7 @@ public function execute($request)
     /**
      * {@inheritDoc}
      */
-    public function supports($request)
+    public function supports($request): bool
     {
         return
             $request instanceof Authorize &&
diff --git a/Action/CancelAction.php b/Action/CancelAction.php
index 81a1b99..0c8e1ac 100644
--- a/Action/CancelAction.php
+++ b/Action/CancelAction.php
@@ -17,7 +17,7 @@ class CancelAction implements ActionInterface
      *
      * @param Cancel $request
      */
-    public function execute($request)
+    public function execute($request): void
     {
         RequestNotSupportedException::assertSupports($this, $request);
 
@@ -29,7 +29,7 @@ public function execute($request)
     /**
      * {@inheritDoc}
      */
-    public function supports($request)
+    public function supports($request): bool
     {
         return
             $request instanceof Cancel &&
diff --git a/Action/CaptureAction.php b/Action/CaptureAction.php
index acbc89f..86429d9 100644
--- a/Action/CaptureAction.php
+++ b/Action/CaptureAction.php
@@ -45,7 +45,7 @@ public function __construct()
     /**
      * @param Capture $request
      */
-    public function execute($request)
+    public function execute($request): void
     {
         RequestNotSupportedException::assertSupports($this, $request);
 
@@ -65,7 +65,7 @@ public function execute($request)
         }
     }
 
-    private function handlePaymentPageInterface(Capture $request)
+    private function handlePaymentPageInterface(Capture $request): void
     {
         $model = ArrayObject::ensureArrayObject($request->getModel());
 
@@ -102,7 +102,7 @@ private function handlePaymentPageInterface(Capture $request)
         }
     }
 
-    private function handleTransactionInterface(Capture $request)
+    private function handleTransactionInterface(Capture $request): void
     {
         $model = ArrayObject::ensureArrayObject($request->getModel());
 
diff --git a/Action/CaptureReferencedAction.php b/Action/CaptureReferencedAction.php
index e431283..0c2f5ab 100644
--- a/Action/CaptureReferencedAction.php
+++ b/Action/CaptureReferencedAction.php
@@ -21,9 +21,9 @@ class CaptureReferencedAction implements ActionInterface, GatewayAwareInterface
     /**
      * @param mixed $request
      *
-     * @throws \Payum\Core\Exception\RequestNotSupportedException if the action dose not support the request.
+     * @throws \Payum\Core\Exception\RequestNotSupportedException if the action does not support the request.
      */
-    public function execute($request)
+    public function execute($request): void
     {
         RequestNotSupportedException::assertSupports($this, $request);
 
@@ -49,10 +49,8 @@ public function execute($request)
 
     /**
      * @param mixed $request
-     *
-     * @return boolean
      */
-    public function supports($request)
+    public function supports($request): bool
     {
         return
             $request instanceof CaptureReferenced &&
diff --git a/Action/ConvertPaymentAction.php b/Action/ConvertPaymentAction.php
index bf87d4b..ed312a8 100644
--- a/Action/ConvertPaymentAction.php
+++ b/Action/ConvertPaymentAction.php
@@ -16,7 +16,7 @@ class ConvertPaymentAction implements ActionInterface
      *
      * @param Convert $request
      */
-    public function execute($request)
+    public function execute($request): void
     {
         RequestNotSupportedException::assertSupports($this, $request);
 
@@ -50,7 +50,7 @@ public function execute($request)
     /**
      * {@inheritDoc}
      */
-    public function supports($request)
+    public function supports($request): bool
     {
         return
             $request instanceof Convert &&
diff --git a/Action/InsertCardAliasAction.php b/Action/InsertCardAliasAction.php
index 391670a..72b3a46 100644
--- a/Action/InsertCardAliasAction.php
+++ b/Action/InsertCardAliasAction.php
@@ -24,7 +24,6 @@ class InsertCardAliasAction implements ActionInterface, GatewayAwareInterface
      */
     public function execute($request): void
     {
-
         RequestNotSupportedException::assertSupports($this, $request);
 
         /** @var $cardAlias CardAliasInterface */
@@ -39,7 +38,7 @@ public function execute($request): void
         }
     }
 
-    private function doExecute(InsertCardAlias $request, ArrayObject $details)
+    private function doExecute(InsertCardAlias $request, ArrayObject $details): void
     {
         if (empty($details['Token'])) {
             $this->insertAliasAction($request, $details);
@@ -48,7 +47,7 @@ private function doExecute(InsertCardAlias $request, ArrayObject $details)
         $this->gateway->execute(new AssertInsertAlias($details));
     }
 
-    private function insertAliasAction(InsertCardAlias $request, ArrayObject $model)
+    private function insertAliasAction(InsertCardAlias $request, ArrayObject $model): void
     {
         if (empty($model['ReturnUrls'])) {
             $token = $request->getToken();
diff --git a/Action/RefundAction.php b/Action/RefundAction.php
index 49cc57d..42ad763 100644
--- a/Action/RefundAction.php
+++ b/Action/RefundAction.php
@@ -20,7 +20,7 @@ class RefundAction implements ActionInterface, GatewayAwareInterface
      *
      * @param Refund $request
      */
-    public function execute($request)
+    public function execute($request): void
     {
         RequestNotSupportedException::assertSupports($this, $request);
 
@@ -33,7 +33,7 @@ public function execute($request)
     /**
      * {@inheritDoc}
      */
-    public function supports($request)
+    public function supports($request): bool
     {
         return
             $request instanceof Refund &&
diff --git a/Action/StatusAction.php b/Action/StatusAction.php
index fd6e0d4..5dfb1c0 100644
--- a/Action/StatusAction.php
+++ b/Action/StatusAction.php
@@ -13,7 +13,7 @@ class StatusAction implements ActionInterface
     /**
      * @param GetStatusInterface $request
      */
-    public function execute($request)
+    public function execute($request): void
     {
         RequestNotSupportedException::assertSupports($this, $request);
 
diff --git a/Api.php b/Api.php
index 78b9ece..7a86cbd 100644
--- a/Api.php
+++ b/Api.php
@@ -45,11 +45,6 @@ class Api
         'optionalParameters' => null,
     );
 
-    /**
-     * @param array               $options
-     * @param HttpClientInterface $client
-     * @param MessageFactory      $messageFactory
-     */
     public function __construct(array $options, HttpClientInterface $client, MessageFactory $messageFactory)
     {
         $options = ArrayObject::ensureArrayObject($options);
@@ -66,13 +61,7 @@ public function __construct(array $options, HttpClientInterface $client, Message
         $this->messageFactory = $messageFactory;
     }
 
-    /**
-     * @param string $path
-     * @param array $fields
-     *
-     * @return array
-     */
-    protected function doRequest($path, array $fields)
+    protected function doRequest(string $path, array $fields): array
     {
         $headers = [
             'Authorization' => 'Basic ' . base64_encode($this->options['username'] . ':' . $this->options['password']),
@@ -235,18 +224,12 @@ public function deleteAlias(string $id): array
         return $this->doRequest(self::ALIAS_DELETE_PATH, $payload);
     }
 
-    /**
-     * @return string
-     */
-    public function getApiEndpoint()
+    public function getApiEndpoint(): string
     {
         return $this->options['sandbox'] ? 'https://test.saferpay.com/api' : 'https://www.saferpay.com/api';
     }
 
-    /**
-     * @return string
-     */
-    public function getCaptureStrategy()
+    public function getCaptureStrategy(): string
     {
         if (isset($this->options['interface']) && is_string($this->options['interface'])) {
             return $this->options['interface'];
@@ -329,12 +312,7 @@ protected function addOptionalInterfaceParams(string $interface, array $payload)
 
         return $payload;
     }
-    
-    /**
-     * @param string $data
-     * @param string $delimiter
-     * @return array
-     */
+
     protected function trimExplode(string $data, string $delimiter = ','): array {
         return array_map('trim', explode($delimiter, $data));
     }
diff --git a/Model/CardAlias.php b/Model/CardAlias.php
index 46d0a02..d5f1ae8 100644
--- a/Model/CardAlias.php
+++ b/Model/CardAlias.php
@@ -18,9 +18,6 @@ public function __construct()
         $this->details = [];
     }
 
-    /**
-     * @return array
-     */
     public function getDetails(): array
     {
         return $this->details;
diff --git a/SaferpayGatewayFactory.php b/SaferpayGatewayFactory.php
index c6bf532..babca62 100644
--- a/SaferpayGatewayFactory.php
+++ b/SaferpayGatewayFactory.php
@@ -30,7 +30,7 @@ class SaferpayGatewayFactory extends GatewayFactory
     /**
      * {@inheritDoc}
      */
-    protected function populateConfig(ArrayObject $config)
+    protected function populateConfig(ArrayObject $config): void
     {
         $config->defaults([
             'payum.factory_name' => 'saferpay',