diff --git a/src/Payment/MollieObject.php b/src/Payment/MollieObject.php
index 7d40e199..b129d8b5 100644
--- a/src/Payment/MollieObject.php
+++ b/src/Payment/MollieObject.php
@@ -4,11 +4,9 @@
 
 namespace Mollie\WooCommerce\Payment;
 
-use Inpsyde\PaymentGateway\PaymentGateway;
 use Mollie\Api\Exceptions\ApiException;
 use Mollie\Api\Resources\Order;
 use Mollie\Api\Resources\Payment;
-use Mollie\WooCommerce\Gateway\MolliePaymentGatewayHandler;
 use Mollie\WooCommerce\Payment\Request\RequestFactory;
 use Mollie\WooCommerce\PaymentMethods\Voucher;
 use Mollie\WooCommerce\SDK\Api;
@@ -17,7 +15,6 @@
 use WC_Order;
 use WC_Payment_Gateway;
 use Psr\Log\LoggerInterface as Logger;
-use stdClass;
 
 class MollieObject
 {
diff --git a/src/Payment/Request/Middleware/AddCustomRequestFieldsMiddleware.php b/src/Payment/Request/Middleware/AddCustomRequestFieldsMiddleware.php
index fde0968a..2ac3de1a 100644
--- a/src/Payment/Request/Middleware/AddCustomRequestFieldsMiddleware.php
+++ b/src/Payment/Request/Middleware/AddCustomRequestFieldsMiddleware.php
@@ -7,18 +7,40 @@
 use Psr\Container\ContainerInterface;
 use WC_Order;
 
+/**
+ * Class AddCustomRequestFieldsMiddleware
+ *
+ * This middleware adds custom request fields to the payment request data.
+ *
+ * @package Mollie\WooCommerce\Payment\Request\Middleware
+ */
 class AddCustomRequestFieldsMiddleware implements RequestMiddlewareInterface
 {
     private array $paymentMethods;
     private ContainerInterface $container;
 
+    /**
+     * AddCustomRequestFieldsMiddleware constructor.
+     *
+     * @param array $paymentMethods An array of available payment methods.
+     * @param ContainerInterface $container A container for dependency injection.
+     */
     public function __construct($paymentMethods, $container)
     {
         $this->paymentMethods = $paymentMethods;
         $this->container = $container;
     }
 
-    public function __invoke(array $requestData, WC_Order $order, $context = null, $next): array
+    /**
+     * Invoke the middleware.
+     *
+     * @param array $requestData The request data to be modified.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param mixed $context Additional context for the middleware.
+     * @param callable $next The next middleware to be called.
+     * @return array The modified request data.
+     */
+    public function __invoke(array $requestData, WC_Order $order, $context, $next): array
     {
         $gateway = wc_get_payment_gateway_by_order($order);
         $methodId = substr($gateway->id, strrpos($gateway->id, '_') + 1);
diff --git a/src/Payment/Request/Middleware/AddSequenceTypeForSubscriptionsMiddleware.php b/src/Payment/Request/Middleware/AddSequenceTypeForSubscriptionsMiddleware.php
index 110c41ff..7713b4d9 100644
--- a/src/Payment/Request/Middleware/AddSequenceTypeForSubscriptionsMiddleware.php
+++ b/src/Payment/Request/Middleware/AddSequenceTypeForSubscriptionsMiddleware.php
@@ -7,18 +7,43 @@
 use Mollie\WooCommerce\Shared\Data;
 use WC_Order;
 
+/**
+ * Middleware to add sequence type for subscription payments.
+ */
 class AddSequenceTypeForSubscriptionsMiddleware implements RequestMiddlewareInterface
 {
+    /**
+     * @var Data Helper class for data operations.
+     */
     private Data $dataHelper;
+
+    /**
+     * @var string Plugin ID.
+     */
     private string $pluginId;
 
+    /**
+     * Constructor.
+     *
+     * @param Data $dataHelper Helper class for data operations.
+     * @param string $pluginId Plugin ID.
+     */
     public function __construct($dataHelper, $pluginId)
     {
         $this->dataHelper = $dataHelper;
         $this->pluginId = $pluginId;
     }
 
-    public function __invoke(array $requestData, WC_Order $order, $context = null, callable $next): array
+    /**
+     * Invoke the middleware.
+     *
+     * @param array $requestData The request data.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $context The context of the request.
+     * @param callable $next The next middleware to call.
+     * @return array The modified request data.
+     */
+    public function __invoke(array $requestData, WC_Order $order, $context, callable $next): array
     {
         $gateway = wc_get_payment_gateway_by_order($order);
         if ($gateway) {
@@ -27,6 +52,15 @@ public function __invoke(array $requestData, WC_Order $order, $context = null, c
         return $next($requestData, $order, $context);
     }
 
+    /**
+     * Add sequence type for the first payments of subscriptions.
+     *
+     * @param int $orderId The order ID.
+     * @param WC_Payment_Gateway $gateway The payment gateway.
+     * @param array $requestData The request data.
+     * @param string $context The context of the request.
+     * @return array The modified request data.
+     */
     private function addSequenceTypeForSubscriptionsFirstPayments($orderId, $gateway, $requestData, $context): array
     {
         if ($this->dataHelper->isSubscription($orderId) || $this->dataHelper->isWcSubscription($orderId)) {
@@ -40,6 +74,13 @@ private function addSequenceTypeForSubscriptionsFirstPayments($orderId, $gateway
         return $requestData;
     }
 
+    /**
+     * Add the sequence type 'first' to the request data.
+     *
+     * @param array $requestData The request data.
+     * @param string $context The context of the request.
+     * @return array The modified request data.
+     */
     private function addSequenceTypeFirst($requestData, $context)
     {
         if ($context === 'order') {
diff --git a/src/Payment/Request/Middleware/AddressMiddleware.php b/src/Payment/Request/Middleware/AddressMiddleware.php
index 0649c537..a9e1498f 100644
--- a/src/Payment/Request/Middleware/AddressMiddleware.php
+++ b/src/Payment/Request/Middleware/AddressMiddleware.php
@@ -7,13 +7,30 @@
 use stdClass;
 use WC_Order;
 
+/**
+ * Class AddressMiddleware
+ *
+ * This middleware adds address information to the payment request data.
+ *
+ * @package Mollie\WooCommerce\Payment\Request\Middleware
+ */
 class AddressMiddleware implements RequestMiddlewareInterface
 {
     public const MAXIMAL_LENGTH_ADDRESS = 100;
     public const MAXIMAL_LENGTH_POSTALCODE = 20;
     public const MAXIMAL_LENGTH_CITY = 200;
     public const MAXIMAL_LENGTH_REGION = 200;
-    public function __invoke(array $requestData, WC_Order $order, $context = null, callable $next): array
+
+    /**
+     * Invoke the middleware.
+     *
+     * @param array<string, mixed> $requestData The request data to be modified.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param mixed $context Additional context for the middleware.
+     * @param callable $next The next middleware to be called.
+     * @return array<string, mixed> The modified request data.
+     */
+    public function __invoke(array $requestData, WC_Order $order, $context, callable $next): array
     {
         $isPayPalExpressOrder = $order->get_meta('_mollie_payment_method_button') === 'PayPalButton';
         $billingAddress = null;
@@ -34,7 +51,13 @@ public function __invoke(array $requestData, WC_Order $order, $context = null, c
         return $next($requestData, $order, $context);
     }
 
-    private function createBillingAddress(WC_Order $order)
+    /**
+     * Create the billing address object.
+     *
+     * @param WC_Order $order The WooCommerce order object.
+     * @return stdClass The billing address object.
+     */
+    private function createBillingAddress(WC_Order $order): stdClass
     {
         // Setup billing and shipping objects
         $billingAddress = new stdClass();
@@ -99,7 +122,13 @@ private function createBillingAddress(WC_Order $order)
         return $billingAddress;
     }
 
-    private function createShippingAddress(WC_Order $order)
+    /**
+     * Create the shipping address object.
+     *
+     * @param WC_Order $order The WooCommerce order object.
+     * @return stdClass The shipping address object.
+     */
+    private function createShippingAddress(WC_Order $order): stdClass
     {
         $shippingAddress = new stdClass();
         // Get user details
@@ -113,7 +142,6 @@ private function createShippingAddress(WC_Order $order)
             ? null
             : $order->get_billing_email(); // WooCommerce doesn't have a shipping email
 
-
         // Create shippingAddress object
         $shippingAddress->streetAndNumber = (ctype_space(
             $order->get_shipping_address_1()
@@ -162,18 +190,29 @@ private function createShippingAddress(WC_Order $order)
         return $shippingAddress;
     }
 
-    protected function getPhoneNumber($order)
+    /**
+     * Get the phone number from the order.
+     *
+     * @param WC_Order $order The WooCommerce order object.
+     * @return string|null The phone number.
+     */
+    protected function getPhoneNumber($order): ?string
     {
-
         $phone = !empty($order->get_billing_phone()) ? $order->get_billing_phone() : $order->get_shipping_phone();
         if (empty($phone)) {
             //phpcs:ignore WordPress.Security.NonceVerification, WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
-            $phone =  wc_clean(wp_unslash($_POST['billing_phone'] ?? ''));
+            $phone = wc_clean(wp_unslash($_POST['billing_phone'] ?? ''));
         }
         return $phone;
     }
 
-    protected function getFormatedPhoneNumber(string $phone)
+    /**
+     * Format the phone number.
+     *
+     * @param string $phone The phone number.
+     * @return string|null The formatted phone number.
+     */
+    protected function getFormatedPhoneNumber(string $phone): ?string
     {
         //remove whitespaces and all non numerical characters except +
         $phone = preg_replace('/[^0-9+]+/', '', $phone);
@@ -191,8 +230,10 @@ protected function getFormatedPhoneNumber(string $phone)
     }
 
     /**
-     * @param $order
-     * @return string|null
+     * Get the billing company field.
+     *
+     * @param WC_Order $order The WooCommerce order object.
+     * @return string|null The billing company field.
      */
     public function billingCompanyField($order): ?string
     {
@@ -205,7 +246,13 @@ public function billingCompanyField($order): ?string
         );
     }
 
-    private function checkBillieCompanyField($order)
+    /**
+     * Check the Billie company field.
+     *
+     * @param WC_Order $order The WooCommerce order object.
+     * @return string|null The Billie company field.
+     */
+    private function checkBillieCompanyField($order): ?string
     {
         $gateway = wc_get_payment_gateway_by_order($order);
         if (!$gateway || !$gateway->id) {
@@ -227,14 +274,13 @@ private function checkBillieCompanyField($order)
     }
 
     /**
-     * Method that shortens the field to a certain length
-     *
-     * @param string $field
-     * @param int    $maximalLength
+     * Method that shortens the field to a certain length.
      *
-     * @return null|string
+     * @param string $field The field to be shortened.
+     * @param int $maximalLength The maximal length of the field.
+     * @return string|null The shortened field.
      */
-    protected function maximalFieldLengths($field, $maximalLength)
+    protected function maximalFieldLengths($field, $maximalLength): ?string
     {
         if (!is_string($field)) {
             return null;
diff --git a/src/Payment/Request/Middleware/ApplePayTokenMiddleware.php b/src/Payment/Request/Middleware/ApplePayTokenMiddleware.php
index a0a2586c..312f1dd3 100644
--- a/src/Payment/Request/Middleware/ApplePayTokenMiddleware.php
+++ b/src/Payment/Request/Middleware/ApplePayTokenMiddleware.php
@@ -6,9 +6,21 @@
 
 use WC_Order;
 
+/**
+ * Middleware to handle Apple Pay token in the request.
+ */
 class ApplePayTokenMiddleware implements RequestMiddlewareInterface
 {
-    public function __invoke(array $requestData, WC_Order $order, $context = null, $next): array
+    /**
+     * Invoke the middleware.
+     *
+     * @param array $requestData The request data.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $context The context of the request.
+     * @param callable $next The next middleware to call.
+     * @return array The modified request data.
+     */
+    public function __invoke(array $requestData, WC_Order $order, $context, $next): array
     {
         // phpcs:ignore WordPress.Security.NonceVerification, WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
         $applePayToken = wc_clean(wp_unslash($_POST["token"] ?? ''));
diff --git a/src/Payment/Request/Middleware/CardTokenMiddleware.php b/src/Payment/Request/Middleware/CardTokenMiddleware.php
index dc95c269..6efa6fe5 100644
--- a/src/Payment/Request/Middleware/CardTokenMiddleware.php
+++ b/src/Payment/Request/Middleware/CardTokenMiddleware.php
@@ -6,9 +6,21 @@
 
 use WC_Order;
 
+/**
+ * Middleware to handle Card Token in the request.
+ */
 class CardTokenMiddleware implements RequestMiddlewareInterface
 {
-    public function __invoke(array $requestData, WC_Order $order, $context = null, $next): array
+    /**
+     * Invoke the middleware.
+     *
+     * @param array $requestData The request data.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $context The context of the request.
+     * @param callable $next The next middleware to call.
+     * @return array The modified request data.
+     */
+    public function __invoke(array $requestData, WC_Order $order, $context, $next): array
     {
         $cardToken = mollieWooCommerceCardToken();
         if ($cardToken && isset($requestData['payment']) && $context === 'order') {
diff --git a/src/Payment/Request/Middleware/CustomerBirthdateMiddleware.php b/src/Payment/Request/Middleware/CustomerBirthdateMiddleware.php
index 9be0d720..1600436b 100644
--- a/src/Payment/Request/Middleware/CustomerBirthdateMiddleware.php
+++ b/src/Payment/Request/Middleware/CustomerBirthdateMiddleware.php
@@ -4,16 +4,36 @@
 
 use WC_Order;
 
+/**
+ * Middleware to handle customer birthdate in the request.
+ */
 class CustomerBirthdateMiddleware implements RequestMiddlewareInterface
 {
+    /**
+     * @var array The payment methods.
+     */
     private array $paymentMethods;
 
+    /**
+     * Constructor.
+     *
+     * @param array $paymentMethods The payment methods.
+     */
     public function __construct(array $paymentMethods)
     {
         $this->paymentMethods = $paymentMethods;
     }
 
-    public function __invoke(array $requestData, WC_Order $order, $context = null, $next): array
+    /**
+     * Invoke the middleware.
+     *
+     * @param array $requestData The request data.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $context The context of the request.
+     * @param callable $next The next middleware to call.
+     * @return array The modified request data.
+     */
+    public function __invoke(array $requestData, WC_Order $order, $context, $next): array
     {
         $gateway = wc_get_payment_gateway_by_order($order);
         if (!$gateway || !isset($gateway->id)) {
@@ -28,7 +48,7 @@ public function __invoke(array $requestData, WC_Order $order, $context = null, $
         $methodId = $additionalFields && in_array('birthdate', $additionalFields, true);
         if ($methodId) {
             $optionName = 'billing_birthdate_' . $paymentMethod->getProperty('id');
-            //phpcs:ignore WordPress.Security.NonceVerification, WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
+            // phpcs:ignore WordPress.Security.NonceVerification, WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
             $fieldPosted = wc_clean(wp_unslash($_POST[$optionName] ?? ''));
             if ($fieldPosted === '' || !is_string($fieldPosted)) {
                 return $requestData;
diff --git a/src/Payment/Request/Middleware/MiddlewareHandler.php b/src/Payment/Request/Middleware/MiddlewareHandler.php
index a22b370d..1a733825 100644
--- a/src/Payment/Request/Middleware/MiddlewareHandler.php
+++ b/src/Payment/Request/Middleware/MiddlewareHandler.php
@@ -4,22 +4,52 @@
 
 use WC_Order;
 
+/**
+ * Class MiddlewareHandler
+ *
+ * This class is responsible for managing and executing a sequence of middleware components.
+ * Each middleware component can modify the request data before it is processed further.
+ *
+ * @package Mollie\WooCommerce\Payment\Request\Middleware
+ */
 class MiddlewareHandler
 {
+    /**
+     * @var array The list of middleware.
+     */
     private array $middlewares;
 
+    /**
+     * MiddlewareHandler constructor.
+     *
+     * @param array $middlewares The list of middleware.
+     */
     public function __construct(array $middlewares)
     {
         $this->middlewares = $middlewares;
     }
 
-    public function handle(array $requestData, WC_Order $order, $context = null): array
+    /**
+     * Handle the request data through the middleware chain.
+     *
+     * @param array $requestData The request data.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $context The context of the request.
+     * @return array The modified request data.
+     */
+    public function handle(array $requestData, WC_Order $order, $context): array
     {
         $middlewareChain = $this->createMiddlewareChain($this->middlewares);
 
         return $middlewareChain($requestData, $order, $context);
     }
 
+    /**
+     * Create a chain of middleware.
+     *
+     * @param array $middlewares The list of middleware.
+     * @return callable The middleware chain.
+     */
     private function createMiddlewareChain(array $middlewares): callable
     {
         return array_reduce(
diff --git a/src/Payment/Request/Middleware/OrderLinesMiddleware.php b/src/Payment/Request/Middleware/OrderLinesMiddleware.php
index ebe5931f..33539e1e 100644
--- a/src/Payment/Request/Middleware/OrderLinesMiddleware.php
+++ b/src/Payment/Request/Middleware/OrderLinesMiddleware.php
@@ -7,18 +7,47 @@
 use Mollie\WooCommerce\Payment\OrderLines;
 use WC_Order;
 
+/**
+ * Class OrderLinesMiddleware
+ *
+ * Middleware to handle order lines in the request.
+ *
+ * @package Mollie\WooCommerce\Payment\Request\Middleware
+ */
 class OrderLinesMiddleware implements RequestMiddlewareInterface
 {
+    /**
+     * @var OrderLines The order lines handler.
+     */
     private OrderLines $orderLines;
+
+    /**
+     * @var string The default category for vouchers.
+     */
     private string $voucherDefaultCategory;
 
-    public function __construct($orderLines, $voucherDefaultCategory)
+    /**
+     * OrderLinesMiddleware constructor.
+     *
+     * @param OrderLines $orderLines The order lines handler.
+     * @param string $voucherDefaultCategory The default category for vouchers.
+     */
+    public function __construct(OrderLines $orderLines, string $voucherDefaultCategory)
     {
         $this->orderLines = $orderLines;
         $this->voucherDefaultCategory = $voucherDefaultCategory;
     }
 
-    public function __invoke(array $requestData, WC_Order $order, $context = null, $next): array
+    /**
+     * Invoke the middleware.
+     *
+     * @param array $requestData The request data.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $context The context of the request.
+     * @param callable $next The next middleware to call.
+     * @return array The modified request data.
+     */
+    public function __invoke(array $requestData, WC_Order $order, $context, $next): array
     {
         $orderLines = $this->orderLines->order_lines($order, $this->voucherDefaultCategory);
         $requestData['lines'] = $orderLines['lines'];
diff --git a/src/Payment/Request/Middleware/PaymentDescriptionMiddleware.php b/src/Payment/Request/Middleware/PaymentDescriptionMiddleware.php
index 1cb29597..1b449157 100644
--- a/src/Payment/Request/Middleware/PaymentDescriptionMiddleware.php
+++ b/src/Payment/Request/Middleware/PaymentDescriptionMiddleware.php
@@ -6,16 +6,40 @@
 
 use WC_Order;
 
+/**
+ * Class PaymentDescriptionMiddleware
+ *
+ * Middleware to handle payment description in the request.
+ *
+ * @package Mollie\WooCommerce\Payment\Request\Middleware
+ */
 class PaymentDescriptionMiddleware implements RequestMiddlewareInterface
 {
+    /**
+     * @var mixed The data helper instance.
+     */
     private $dataHelper;
 
+    /**
+     * PaymentDescriptionMiddleware constructor.
+     *
+     * @param mixed $dataHelper The data helper instance.
+     */
     public function __construct($dataHelper)
     {
         $this->dataHelper = $dataHelper;
     }
 
-    public function __invoke(array $requestData, WC_Order $order, string $context = null, $next): array
+    /**
+     * Invoke the middleware.
+     *
+     * @param array $requestData The request data.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $context The context of the request.
+     * @param callable $next The next middleware to call.
+     * @return array The modified request data.
+     */
+    public function __invoke(array $requestData, WC_Order $order, string $context, $next): array
     {
         $optionName = $this->dataHelper->getPluginId() . '_' . 'api_payment_description';
         $option = get_option($optionName);
@@ -25,75 +49,74 @@ public function __invoke(array $requestData, WC_Order $order, string $context =
         return $next($requestData, $order, $context);
     }
 
+    /**
+     * Get the payment description.
+     *
+     * @param WC_Order $order The WooCommerce order object.
+     * @param mixed $option The option value.
+     * @return string The payment description.
+     */
     private function getPaymentDescription(WC_Order $order, $option): string
     {
         $description = !$option ? '' : trim($option);
         $description = !$description ? '{orderNumber}' : $description;
 
         switch ($description) {
-            // Support for old deprecated options.
-            // TODO: remove when deprecated
             case '{orderNumber}':
-                $description =
-                    /* translators: do not translate between {} */
-                    _x(
-                        'Order {orderNumber}',
-                        'Payment description for {orderNumber}',
-                        'mollie-payments-for-woocommerce'
-                    );
+                $description = _x(
+                    'Order {orderNumber}',
+                    'Payment description for {orderNumber}',
+                    'mollie-payments-for-woocommerce'
+                );
                 $description = $this->replaceTagsDescription($order, $description);
                 break;
             case '{storeName}':
-                $description =
-                    /* translators: do not translate between {} */
-                    _x(
-                        'StoreName {storeName}',
-                        'Payment description for {storeName}',
-                        'mollie-payments-for-woocommerce'
-                    );
+                $description = _x(
+                    'StoreName {storeName}',
+                    'Payment description for {storeName}',
+                    'mollie-payments-for-woocommerce'
+                );
                 $description = $this->replaceTagsDescription($order, $description);
                 break;
             case '{customer.firstname}':
-                $description =
-                    /* translators: do not translate between {} */
-                    _x(
-                        'Customer Firstname {customer.firstname}',
-                        'Payment description for {customer.firstname}',
-                        'mollie-payments-for-woocommerce'
-                    );
+                $description = _x(
+                    'Customer Firstname {customer.firstname}',
+                    'Payment description for {customer.firstname}',
+                    'mollie-payments-for-woocommerce'
+                );
                 $description = $this->replaceTagsDescription($order, $description);
                 break;
             case '{customer.lastname}':
-                $description =
-                    /* translators: do not translate between {} */
-                    _x(
-                        'Customer Lastname {customer.lastname}',
-                        'Payment description for {customer.lastname}',
-                        'mollie-payments-for-woocommerce'
-                    );
+                $description = _x(
+                    'Customer Lastname {customer.lastname}',
+                    'Payment description for {customer.lastname}',
+                    'mollie-payments-for-woocommerce'
+                );
                 $description = $this->replaceTagsDescription($order, $description);
                 break;
             case '{customer.company}':
-                $description =
-                    /* translators: do not translate between {} */
-                    _x(
-                        'Customer Company {customer.company}',
-                        'Payment description for {customer.company}',
-                        'mollie-payments-for-woocommerce'
-                    );
+                $description = _x(
+                    'Customer Company {customer.company}',
+                    'Payment description for {customer.company}',
+                    'mollie-payments-for-woocommerce'
+                );
                 $description = $this->replaceTagsDescription($order, $description);
                 break;
-            // Support for custom string with interpolation.
             default:
-                // Replace available description tags.
                 $description = $this->replaceTagsDescription($order, $description);
                 break;
         }
 
-        // Fall back on default if description turns out empty.
         return !$description ? __('Order', 'woocommerce') . ' ' . $order->get_order_number() : $description;
     }
 
+    /**
+     * Replace tags in the description with actual values.
+     *
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $description The description with tags.
+     * @return string The description with tags replaced.
+     */
     private function replaceTagsDescription(WC_Order $order, string $description): string
     {
         $replacement_tags = [
diff --git a/src/Payment/Request/Middleware/RequestMiddlewareInterface.php b/src/Payment/Request/Middleware/RequestMiddlewareInterface.php
index 51ff8a95..52e595f6 100644
--- a/src/Payment/Request/Middleware/RequestMiddlewareInterface.php
+++ b/src/Payment/Request/Middleware/RequestMiddlewareInterface.php
@@ -6,5 +6,14 @@
 
 interface RequestMiddlewareInterface
 {
-    public function __invoke(array $requestData, WC_Order $order, string $context = null, callable $next): array;
+    /**
+     * Invoke the middleware.
+     *
+     * @param array<string, mixed> $requestData The request data to be modified.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $context Additional context for the middleware.
+     * @param callable $next The next middleware to be called.
+     * @return array<string, mixed> The modified request data.
+     */
+    public function __invoke(array $requestData, WC_Order $order, string $context, callable $next): array;
 }
diff --git a/src/Payment/Request/Middleware/SelectedIssuerMiddleware.php b/src/Payment/Request/Middleware/SelectedIssuerMiddleware.php
index b889d36f..5dc30659 100644
--- a/src/Payment/Request/Middleware/SelectedIssuerMiddleware.php
+++ b/src/Payment/Request/Middleware/SelectedIssuerMiddleware.php
@@ -6,21 +6,43 @@
 
 use WC_Order;
 
+/**
+ * Class SelectedIssuerMiddleware
+ *
+ * Middleware to handle the selection of the payment issuer.
+ *
+ * @package Mollie\WooCommerce\Payment\Request\Middleware
+ */
 class SelectedIssuerMiddleware implements RequestMiddlewareInterface
 {
+    /**
+     * @var string The plugin ID.
+     */
     private $pluginId;
 
-    public function __construct($pluginId)
+    /**
+     * SelectedIssuerMiddleware constructor.
+     *
+     * @param string $pluginId The plugin ID.
+     */
+    public function __construct(string $pluginId)
     {
         $this->pluginId = $pluginId;
     }
 
-    public function __invoke(array $requestData, WC_Order $order, $context = null, $next): array
+    /**
+     * Invoke the middleware.
+     *
+     * @param array<string, mixed> $requestData The request data to be modified.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $context Additional context for the middleware.
+     * @param callable $next The next middleware to be called.
+     * @return array<string, mixed> The modified request data.
+     */
+    public function __invoke(array $requestData, WC_Order $order, string $context, callable $next): array
     {
-
         $gateway = wc_get_payment_gateway_by_order($order);
         if (!$gateway) {
-
             return $next($requestData, $order, $context);
         }
 
@@ -29,6 +51,7 @@ public function __invoke(array $requestData, WC_Order $order, $context = null, $
         if (empty($selectedIssuer)) {
             return $next($requestData, $order, $context);
         }
+
         if ($context === 'order') {
             $requestData['payment']['issuer'] = $selectedIssuer;
         } elseif ($context === 'payment') {
@@ -38,10 +61,16 @@ public function __invoke(array $requestData, WC_Order $order, $context = null, $
         return $next($requestData, $order, $context);
     }
 
+    /**
+     * Get the selected issuer.
+     *
+     * @param string $gatewayId The payment gateway ID.
+     * @return string The selected issuer.
+     */
     private function getSelectedIssuer(string $gatewayId): string
     {
         $issuer_id = $this->pluginId . '_issuer_' . $gatewayId;
-        //phpcs:ignore WordPress.Security.NonceVerification, WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
+        // phpcs:ignore WordPress.Security.NonceVerification, WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
         $postedIssuer = wc_clean(wp_unslash($_POST[$issuer_id] ?? ''));
         return !empty($postedIssuer) ? $postedIssuer : '';
     }
diff --git a/src/Payment/Request/Middleware/StoreCustomerMiddleware.php b/src/Payment/Request/Middleware/StoreCustomerMiddleware.php
index 375c6bbf..45e24cef 100644
--- a/src/Payment/Request/Middleware/StoreCustomerMiddleware.php
+++ b/src/Payment/Request/Middleware/StoreCustomerMiddleware.php
@@ -7,15 +7,40 @@
 use Mollie\WooCommerce\Settings\Settings;
 use WC_Order;
 
+/**
+ * Class StoreCustomerMiddleware
+ *
+ * Middleware to handle the storage of customer information.
+ *
+ * @package Mollie\WooCommerce\Payment\Request\Middleware
+ */
 class StoreCustomerMiddleware implements RequestMiddlewareInterface
 {
+    /**
+     * @var Settings The settings helper instance.
+     */
     private Settings $settingsHelper;
+
+    /**
+     * StoreCustomerMiddleware constructor.
+     *
+     * @param Settings $settingsHelper The settings helper instance.
+     */
     public function __construct(Settings $settingsHelper)
     {
         $this->settingsHelper = $settingsHelper;
     }
 
-    public function __invoke(array $requestData, WC_Order $order, $context = null, $next): array
+    /**
+     * Invoke the middleware.
+     *
+     * @param array<string, mixed> $requestData The request data to be modified.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $context Additional context for the middleware.
+     * @param callable $next The next middleware to be called.
+     * @return array<string, mixed> The modified request data.
+     */
+    public function __invoke(array $requestData, WC_Order $order, string $context, callable $next): array
     {
         $storeCustomer = $this->settingsHelper->shouldStoreCustomer();
         if (!$storeCustomer) {
diff --git a/src/Payment/Request/Middleware/UrlMiddleware.php b/src/Payment/Request/Middleware/UrlMiddleware.php
index 82d03b1a..464b9285 100644
--- a/src/Payment/Request/Middleware/UrlMiddleware.php
+++ b/src/Payment/Request/Middleware/UrlMiddleware.php
@@ -6,21 +6,47 @@
 
 use WC_Order;
 
+/**
+ * Class UrlMiddleware
+ *
+ * Middleware to handle URL modifications for payment requests.
+ *
+ * @package Mollie\WooCommerce\Payment\Request\Middleware
+ */
 class UrlMiddleware implements RequestMiddlewareInterface
 {
+    /**
+     * @var string The plugin ID.
+     */
     private $pluginId;
+
     /**
-     * @var mixed
+     * @var mixed The logger instance.
      */
     private $logger;
 
+    /**
+     * UrlMiddleware constructor.
+     *
+     * @param string $pluginId The plugin ID.
+     * @param mixed $logger The logger instance.
+     */
     public function __construct($pluginId, $logger)
     {
         $this->pluginId = $pluginId;
         $this->logger = $logger;
     }
 
-    public function __invoke(array $requestData, WC_Order $order, $context = null, $next): array
+    /**
+     * Invoke the middleware.
+     *
+     * @param array<string, mixed> $requestData The request data to be modified.
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $context Additional context for the middleware.
+     * @param callable $next The next middleware to be called.
+     * @return array<string, mixed> The modified request data.
+     */
+    public function __invoke(array $requestData, WC_Order $order, $context, $next): array
     {
         $gateway = wc_get_payment_gateway_by_order($order);
         if ($gateway) {
@@ -35,15 +61,15 @@ public function __invoke(array $requestData, WC_Order $order, $context = null, $
     }
 
     /**
-     * Get the url to return to on Mollie return
-     * saves the return redirect and failed redirect, so we save the page language in case there is one set
-     * For example 'http://mollie-wc.docker.myhost/wc-api/mollie_return/?order_id=89&key=wc_order_eFZyH8jki6fge'
+     * Get the URL to return to on Mollie return.
+     * Saves the return redirect and failed redirect, so we save the page language in case there is one set.
+     * For example 'http://mollie-wc.docker.myhost/wc-api/mollie_return/?order_id=89&key=wc_order_eFZyH8jki6fge'.
      *
-     * @param WC_Order $order The order processed
-     *
-     * @return string The url with order id and key as params
+     * @param WC_Order $order The order processed.
+     * @param string $returnUrl The base return URL.
+     * @return string The URL with order ID and key as params.
      */
-    private function getReturnUrl($order, $returnUrl)
+    private function getReturnUrl(WC_Order $order, string $returnUrl): string
     {
         $returnUrl = untrailingslashit($returnUrl);
         $returnUrl = $this->asciiDomainName($returnUrl);
@@ -64,14 +90,14 @@ private function getReturnUrl($order, $returnUrl)
     }
 
     /**
-     * Get the webhook url
-     * For example 'http://mollie-wc.docker.myhost/wc-api/mollie_return/mollie_wc_gateway_bancontact/?order_id=89&key=wc_order_eFZyH8jki6fge'
-     *
-     * @param WC_Order $order The order processed
+     * Get the webhook URL.
+     * For example 'http://mollie-wc.docker.myhost/wc-api/mollie_return/mollie_wc_gateway_bancontact/?order_id=89&key=wc_order_eFZyH8jki6fge'.
      *
-     * @return string The url with gateway and order id and key as params
+     * @param WC_Order $order The order processed.
+     * @param string $gatewayId The payment gateway ID.
+     * @return string The URL with gateway and order ID and key as params.
      */
-    public function getWebhookUrl($order, $gatewayId)
+    public function getWebhookUrl(WC_Order $order, string $gatewayId): string
     {
         $webhookUrl = WC()->api_request_url($gatewayId);
         $webhookUrl = untrailingslashit($webhookUrl);
@@ -91,11 +117,12 @@ public function getWebhookUrl($order, $gatewayId)
     }
 
     /**
-     * @param $url
+     * Convert the domain name in a URL to ASCII.
      *
-     * @return string
+     * @param string $url The URL to convert.
+     * @return string The URL with the domain name in ASCII.
      */
-    protected function asciiDomainName($url): string
+    protected function asciiDomainName(string $url): string
     {
         $parsed = wp_parse_url($url);
         $scheme = isset($parsed['scheme']) ? $parsed['scheme'] : '';
@@ -113,15 +140,17 @@ protected function asciiDomainName($url): string
 
         return $url;
     }
+
     /**
-     * @param $order_id
-     * @param $order_key
-     * @param $webhook_url
-     * @param string $filterFlag
+     * Append order arguments to a URL.
      *
-     * @return string
+     * @param int $order_id The order ID.
+     * @param string $order_key The order key.
+     * @param string $webhook_url The base webhook URL.
+     * @param string $filterFlag An optional filter flag.
+     * @return string The URL with appended order arguments.
      */
-    protected function appendOrderArgumentsToUrl($order_id, $order_key, $webhook_url, $filterFlag = '')
+    protected function appendOrderArgumentsToUrl(int $order_id, string $order_key, string $webhook_url, string $filterFlag = ''): string
     {
         $webhook_url = add_query_arg(
             [
@@ -133,17 +162,18 @@ protected function appendOrderArgumentsToUrl($order_id, $order_key, $webhook_url
         );
         return $webhook_url;
     }
+
     /**
-     * @param $domain
-     * @return false|mixed|string
+     * Encode a domain name to ASCII.
+     *
+     * @param string $domain The domain name to encode.
+     * @return string The encoded domain name.
      */
-    protected function idnEncodeDomain($domain)
+    protected function idnEncodeDomain(string $domain): string
     {
         if (
             defined('IDNA_NONTRANSITIONAL_TO_ASCII')
-            && defined(
-                'INTL_IDNA_VARIANT_UTS46'
-            )
+            && defined('INTL_IDNA_VARIANT_UTS46')
         ) {
             $domain = idn_to_ascii(
                 $domain,
diff --git a/src/Payment/Request/RequestFactory.php b/src/Payment/Request/RequestFactory.php
index a581daff..1f67f4ce 100644
--- a/src/Payment/Request/RequestFactory.php
+++ b/src/Payment/Request/RequestFactory.php
@@ -6,23 +6,38 @@
 use Psr\Container\ContainerInterface;
 use WC_Order;
 
+/**
+ * Class RequestFactory
+ *
+ * This class is responsible for creating payment requests based on the provided type.
+ *
+ * @package Mollie\WooCommerce\Payment\Request
+ */
 class RequestFactory
 {
-    private $container;
+    /**
+     * @var ContainerInterface The container interface for dependency injection.
+     */
+    private ContainerInterface $container;
 
+    /**
+     * RequestFactory constructor.
+     *
+     * @param ContainerInterface $container The container interface for dependency injection.
+     */
     public function __construct(ContainerInterface $container)
     {
-
         $this->container = $container;
     }
 
     /**
      * Create a request based on the type.
      *
-     * @param string $type 'order' or 'payment'.
+     * @param string $type The type of request ('order' or 'payment').
      * @param WC_Order $order The WooCommerce order object.
-     * @param string|null $customerId Customer ID for the request.
+     * @param string|null $customerId The customer ID for the request.
      * @return array The generated request data.
+     * @throws \InvalidArgumentException If the strategy for the given type is invalid.
      */
     public function createRequest(string $type, WC_Order $order, $customerId): array
     {
diff --git a/src/Payment/Request/Strategies/OrderRequestStrategy.php b/src/Payment/Request/Strategies/OrderRequestStrategy.php
index 6d96719c..390c0fc5 100644
--- a/src/Payment/Request/Strategies/OrderRequestStrategy.php
+++ b/src/Payment/Request/Strategies/OrderRequestStrategy.php
@@ -2,26 +2,56 @@
 
 namespace Mollie\WooCommerce\Payment\Request\Strategies;
 
-use Inpsyde\PaymentGateway\PaymentGateway;
 use Mollie\WooCommerce\Payment\Request\Middleware\MiddlewareHandler;
 use Mollie\WooCommerce\Settings\Settings;
 use Mollie\WooCommerce\Shared\Data;
 use WC_Order;
 
+/**
+ * Class OrderRequestStrategy
+ *
+ * This class handles the creation of payment requests for the Mollie orders API.
+ *
+ * @package Mollie\WooCommerce\Payment\Request\Strategies
+ */
 class OrderRequestStrategy implements RequestStrategyInterface
 {
+    /**
+     * @var Data
+     */
     private Data $dataHelper;
+
+    /**
+     * @var Settings
+     */
     private Settings $settingsHelper;
+
+    /**
+     * @var MiddlewareHandler
+     */
     private MiddlewareHandler $middlewareHandler;
 
+    /**
+     * OrderRequestStrategy constructor.
+     *
+     * @param Data $dataHelper
+     * @param Settings $settingsHelper
+     * @param MiddlewareHandler $middlewareHandler
+     */
     public function __construct($dataHelper, $settingsHelper, MiddlewareHandler $middlewareHandler)
     {
-
         $this->dataHelper = $dataHelper;
         $this->settingsHelper = $settingsHelper;
         $this->middlewareHandler = $middlewareHandler;
     }
 
+    /**
+     * Create a payment request for the given order.
+     *
+     * @param WC_Order $order The order to create a request for.
+     * @param string $customerId The customer ID.
+     * @return array The request data.
+     */
     public function createRequest(WC_Order $order, $customerId): array
     {
         $settingsHelper = $this->settingsHelper;
@@ -34,7 +64,6 @@ public function createRequest(WC_Order $order, $customerId): array
 
         $methodId = substr($gateway->id, strrpos($gateway->id, '_') + 1);
         $paymentLocale = $settingsHelper->getPaymentLocale();
-        // Build the Mollie order data
         $requestData = [
             'amount' => [
                 'currency' => $this->dataHelper->getOrderCurrency($order),
diff --git a/src/Payment/Request/Strategies/PaymentRequestStrategy.php b/src/Payment/Request/Strategies/PaymentRequestStrategy.php
index 0ff4e94d..749923e2 100644
--- a/src/Payment/Request/Strategies/PaymentRequestStrategy.php
+++ b/src/Payment/Request/Strategies/PaymentRequestStrategy.php
@@ -4,45 +4,74 @@
 
 use Inpsyde\PaymentGateway\PaymentGateway;
 use Mollie\WooCommerce\Payment\Request\Middleware\MiddlewareHandler;
+use Mollie\WooCommerce\Settings\Settings;
+use Mollie\WooCommerce\Shared\Data;
 use WC_Order;
 
+/**
+ * Class PaymentRequestStrategy
+ *
+ * This class handles the creation of payment requests for the Mollie payments API.
+ *
+ * @package Mollie\WooCommerce\Payment\Request\Strategies
+ */
 class PaymentRequestStrategy implements RequestStrategyInterface
 {
-    private $dataHelper;
-    private $settingsHelper;
+    /**
+     * @var Data Helper for data operations.
+     */
+    private Data $dataHelper;
+
+    /**
+     * @var Settings Helper for settings operations.
+     */
+    private Settings $settingsHelper;
+
+    /**
+     * @var MiddlewareHandler Handler for middleware operations.
+     */
     private MiddlewareHandler $middlewareHandler;
 
+    /**
+     * PaymentRequestStrategy constructor.
+     *
+     * @param Data $dataHelper Helper for data operations.
+     * @param Settings $settingsHelper Helper for settings operations.
+     * @param MiddlewareHandler $middlewareHandler Handler for middleware operations.
+     */
     public function __construct($dataHelper, $settingsHelper, MiddlewareHandler $middlewareHandler)
     {
-
         $this->dataHelper = $dataHelper;
         $this->settingsHelper = $settingsHelper;
         $this->middlewareHandler = $middlewareHandler;
     }
 
+    /**
+     * Create a payment request for the given order.
+     *
+     * @param WC_Order $order The order to create a request for.
+     * @param string $customerId The customer ID.
+     * @return array The request data.
+     */
     public function createRequest(WC_Order $order, $customerId): array
     {
-
         $gateway = wc_get_payment_gateway_by_order($order);
 
         if (!$gateway || !(mollieWooCommerceIsMollieGateway($gateway->id))) {
             return ['result' => 'failure'];
         }
+
         $settingsHelper = $this->settingsHelper;
         $methodId = substr($gateway->id, strrpos($gateway->id, '_') + 1);
         $paymentLocale = $settingsHelper->getPaymentLocale();
 
         $requestData = [
             'amount' => [
-                'currency' => $this->dataHelper
-                    ->getOrderCurrency($order),
-                'value' => $this->dataHelper
-                    ->formatCurrencyValue(
-                        $order->get_total(),
-                        $this->dataHelper->getOrderCurrency(
-                            $order
-                        )
-                    ),
+                'currency' => $this->dataHelper->getOrderCurrency($order),
+                'value' => $this->dataHelper->formatCurrencyValue(
+                    $order->get_total(),
+                    $this->dataHelper->getOrderCurrency($order)
+                ),
             ],
             'method' => $methodId,
             'locale' => $paymentLocale,
diff --git a/src/Payment/Request/Strategies/RequestStrategyInterface.php b/src/Payment/Request/Strategies/RequestStrategyInterface.php
index 288af22f..631ecb75 100644
--- a/src/Payment/Request/Strategies/RequestStrategyInterface.php
+++ b/src/Payment/Request/Strategies/RequestStrategyInterface.php
@@ -4,7 +4,21 @@
 
 use WC_Order;
 
+/**
+ * Interface RequestStrategyInterface
+ *
+ * Defines the contract for creating payment requests.
+ *
+ * @package Mollie\WooCommerce\Payment\Request\Strategies
+ */
 interface RequestStrategyInterface
 {
-    public function createRequest(WC_Order $order, $customerId): array;
+    /**
+     * Creates a payment request.
+     *
+     * @param WC_Order $order The WooCommerce order object.
+     * @param string $customerId The customer ID.
+     * @return array The payment request data.
+     */
+    public function createRequest(WC_Order $order, string $customerId): array;
 }