diff --git a/composer.json b/composer.json
index 8451004..362c5cc 100644
--- a/composer.json
+++ b/composer.json
@@ -3,7 +3,7 @@
   "license": "OSL-3.0",
   "description": "Robin HQ library",
   "require": {
-    "php": ">=8.0 <=8.3",
+    "php": ">=8.0 <=8.4",
     "guzzlehttp/guzzle": "^7.4",
     "psr/log": "*",
     "psr/container": "^1.0|^2.0",
diff --git a/src/Client/RobinClient.php b/src/Client/RobinClient.php
index a208d0e..be5f56a 100644
--- a/src/Client/RobinClient.php
+++ b/src/Client/RobinClient.php
@@ -14,6 +14,7 @@
 use Emico\RobinHqLib\Model\Customer;
 use Emico\RobinHqLib\Model\Order;
 use GuzzleHttp\Client;
+use GuzzleHttp\Utils;
 use JsonSerializable;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Log\LoggerInterface;
@@ -112,7 +113,7 @@ public function postDynamicCustomer(Customer $customer): ResponseInterface
      */
     protected function post(string $path, $payload): ResponseInterface
     {
-        $this->logger->debug('Payload: ' . \GuzzleHttp\json_encode($payload));
+        $this->logger->debug('Payload: ' . Utils::jsonEncode($payload));
 
         $response = $this->httpClient->post($path, [
             'auth' => [ $this->config->getApiKey(), $this->config->getApiSecret() ],
diff --git a/src/Client/RobinClientFactory.php b/src/Client/RobinClientFactory.php
index 02c7033..3df078a 100644
--- a/src/Client/RobinClientFactory.php
+++ b/src/Client/RobinClientFactory.php
@@ -8,7 +8,6 @@
 
 
 use Emico\RobinHqLib\Config\Config;
-use GuzzleHttp\Client;
 use Psr\Container\ContainerExceptionInterface;
 use Psr\Container\ContainerInterface;
 use Psr\Container\NotFoundExceptionInterface;
@@ -33,4 +32,4 @@ public function __invoke(ContainerInterface $container): RobinClient
 
         return new RobinClient($config, $container->get(LoggerInterface::class));
     }
-}
\ No newline at end of file
+}
diff --git a/src/EventProcessor/CustomerEventProcessor.php b/src/EventProcessor/CustomerEventProcessor.php
index 2646b46..1045e95 100644
--- a/src/EventProcessor/CustomerEventProcessor.php
+++ b/src/EventProcessor/CustomerEventProcessor.php
@@ -10,8 +10,6 @@
 use Emico\RobinHqLib\Client\RobinClient;
 use Emico\RobinHqLib\Event\CustomerEvent;
 use Emico\RobinHqLib\Event\EventInterface;
-use Exception;
-use Psr\Log\LoggerInterface;
 
 class CustomerEventProcessor implements EventProcessorInterface
 {
@@ -32,4 +30,4 @@ public function processEvent(EventInterface $event): bool
         $this->robinClient->postDynamicCustomer($event->getCustomer());
         return true;
     }
-}
\ No newline at end of file
+}
diff --git a/src/EventProcessor/CustomerEventProcessorFactory.php b/src/EventProcessor/CustomerEventProcessorFactory.php
index e405f19..a9d4929 100644
--- a/src/EventProcessor/CustomerEventProcessorFactory.php
+++ b/src/EventProcessor/CustomerEventProcessorFactory.php
@@ -8,11 +8,9 @@
 
 
 use Emico\RobinHqLib\Client\RobinClient;
-use Emico\RobinHqLib\Queue\EventInterface;
 use Psr\Container\ContainerExceptionInterface;
 use Psr\Container\ContainerInterface;
 use Psr\Container\NotFoundExceptionInterface;
-use Psr\Log\LoggerInterface;
 
 class CustomerEventProcessorFactory
 {
@@ -26,4 +24,4 @@ public function __invoke(ContainerInterface $container): CustomerEventProcessor
     {
         return new CustomerEventProcessor($container->get(RobinClient::class));
     }
-}
\ No newline at end of file
+}
diff --git a/src/EventProcessor/OrderEventProcessor.php b/src/EventProcessor/OrderEventProcessor.php
index 4136e29..f01f7c5 100644
--- a/src/EventProcessor/OrderEventProcessor.php
+++ b/src/EventProcessor/OrderEventProcessor.php
@@ -10,7 +10,6 @@
 use Emico\RobinHqLib\Client\RobinClient;
 use Emico\RobinHqLib\Event\EventInterface;
 use Emico\RobinHqLib\Event\OrderEvent;
-use Psr\Log\LoggerInterface;
 
 class OrderEventProcessor implements EventProcessorInterface
 {
@@ -31,4 +30,4 @@ public function processEvent(EventInterface $event): bool
         $this->robinClient->postDynamicOrder($event->getOrder());
         return true;
     }
-}
\ No newline at end of file
+}
diff --git a/src/Model/Collection.php b/src/Model/Collection.php
index 2a201dd..8ee7309 100644
--- a/src/Model/Collection.php
+++ b/src/Model/Collection.php
@@ -24,7 +24,7 @@ class Collection implements JsonSerializable, \Countable
     /**
      * Collection constructor.
      * @param array $elements
-     * @param string $key
+     * @param null|string $key
      */
     public function __construct(array $elements, string $key = null)
     {
diff --git a/src/Model/Customer.php b/src/Model/Customer.php
index 71f810f..217b62b 100644
--- a/src/Model/Customer.php
+++ b/src/Model/Customer.php
@@ -6,7 +6,6 @@
 
 namespace Emico\RobinHqLib\Model;
 
-use DateTime;
 use DateTimeInterface;
 use Emico\RobinHqLib\Config\Config;
 use JsonSerializable;
@@ -242,7 +241,7 @@ public function jsonSerialize()
             'email_address' => $this->emailAddress,
             'name' => $this->name,
             'phone_number' => $this->phoneNumber,
-            'customer_since' => $this->customerSince ? $this->customerSince->format(DateTime::ISO8601) : '',
+            'customer_since' => $this->customerSince ? $this->customerSince->format(\DateTimeInterface::ISO8601) : '',
             'order_count' => $this->orderCount,
             'total_revenue' => $this->totalRevenue,
             'total_spent' => (string) $this->totalRevenue,
diff --git a/src/Model/Order.php b/src/Model/Order.php
index 893300d..a02f8bf 100644
--- a/src/Model/Order.php
+++ b/src/Model/Order.php
@@ -7,11 +7,9 @@
 namespace Emico\RobinHqLib\Model;
 
 
-use DateTime;
 use DateTimeInterface;
 use Emico\RobinHqLib\Config\Config;
 use Emico\RobinHqLib\Model\Order\DetailsView;
-use PhpOffice\PhpSpreadsheet\Shared\Date;
 
 class Order implements \JsonSerializable
 {
diff --git a/src/Model/Order/DetailsView.php b/src/Model/Order/DetailsView.php
index 3026d58..9ef3f1e 100644
--- a/src/Model/Order/DetailsView.php
+++ b/src/Model/Order/DetailsView.php
@@ -7,7 +7,6 @@
 namespace Emico\RobinHqLib\Model\Order;
 
 use DateTimeInterface;
-use Emico\RobinHqLib\Config\Config;
 use JsonSerializable;
 
 class DetailsView implements JsonSerializable
diff --git a/src/Model/SearchResult.php b/src/Model/SearchResult.php
index 9891d92..074706e 100644
--- a/src/Model/SearchResult.php
+++ b/src/Model/SearchResult.php
@@ -7,9 +7,6 @@
 namespace Emico\RobinHqLib\Model;
 
 
-use DateTime;
-use DateTimeInterface;
-
 class SearchResult implements \JsonSerializable
 {
     /**
diff --git a/src/Queue/FileQueueFactory.php b/src/Queue/FileQueueFactory.php
index 8b81ad2..bc5fe2d 100644
--- a/src/Queue/FileQueueFactory.php
+++ b/src/Queue/FileQueueFactory.php
@@ -22,12 +22,10 @@ class FileQueueFactory
      */
     public function __invoke(ContainerInterface $container): FileQueue
     {
-        $queue = new FileQueue(
+        return new FileQueue(
             __DIR__ . '/../../var/queue',
             $container->get(EventProcessingService::class),
             $container->get(LoggerInterface::class)
         );
-
-        return $queue;
     }
-}
\ No newline at end of file
+}
diff --git a/src/Queue/QueueInterface.php b/src/Queue/QueueInterface.php
index 849f9c0..2012fd2 100644
--- a/src/Queue/QueueInterface.php
+++ b/src/Queue/QueueInterface.php
@@ -7,13 +7,11 @@
 namespace Emico\RobinHqLib\Queue;
 
 
-use Emico\RobinHqLib\Service\EventProcessingService;
-
 interface QueueInterface
 {
     /**
-     * @param string $event
+     * @param string $serializedEvent
      * @return bool
      */
-    public function pushEvent(string $event): bool;
-}
\ No newline at end of file
+    public function pushEvent(string $serializedEvent): bool;
+}
diff --git a/src/Server/RestApiServer.php b/src/Server/RestApiServer.php
index 4d5a3d5..f31d93d 100644
--- a/src/Server/RestApiServer.php
+++ b/src/Server/RestApiServer.php
@@ -12,9 +12,9 @@
 use Emico\RobinHqLib\DataProvider\Exception\DataNotFoundException;
 use Emico\RobinHqLib\DataProvider\Exception\InvalidRequestException;
 use Exception;
+use Laminas\Diactoros\Response\JsonResponse;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
-use Laminas\Diactoros\Response\JsonResponse;
 
 class RestApiServer
 {
@@ -71,7 +71,7 @@ protected function authenticateRequest(ServerRequestInterface $request): bool
         /* If using PHP in CGI mode. */
         if (isset($serverParams['HTTP_AUTHORIZATION'])) {
             if (preg_match("/Basic\s+(.*)$/i", $serverParams['HTTP_AUTHORIZATION'], $matches)) {
-                list($user, $password) = explode(':', base64_decode($matches[1]), 2);
+                [$user, $password] = explode(':', base64_decode($matches[1]), 2);
             }
         } else {
             if (isset($serverParams["PHP_AUTH_USER"])) {
@@ -88,4 +88,4 @@ protected function authenticateRequest(ServerRequestInterface $request): bool
 
         return true;
     }
-}
\ No newline at end of file
+}
diff --git a/src/Service/CustomerServiceFactory.php b/src/Service/CustomerServiceFactory.php
index 33588c5..a16d023 100644
--- a/src/Service/CustomerServiceFactory.php
+++ b/src/Service/CustomerServiceFactory.php
@@ -7,16 +7,10 @@
 namespace Emico\RobinHqLib\Service;
 
 
-use Emico\RobinHqLib\Client\RobinClient;
-use Emico\RobinHqLib\EventProcessor\CustomerEventProcessor;
-use Emico\RobinHqLib\EventProcessor\OrderEventProcessor;
 use Emico\RobinHqLib\Queue\QueueInterface;
-use Emico\RobinHqLib\Queue\Serializer\EventSerializer;
 use Psr\Container\ContainerExceptionInterface;
 use Psr\Container\ContainerInterface;
 use Psr\Container\NotFoundExceptionInterface;
-use Psr\Log\LoggerInterface;
-use Psr\Log\NullLogger;
 
 class CustomerServiceFactory
 {
@@ -30,4 +24,4 @@ public function __invoke(ContainerInterface $container): CustomerService
     {
         return new CustomerService($container->get(QueueInterface::class));
     }
-}
\ No newline at end of file
+}
diff --git a/src/Service/EventProcessingService.php b/src/Service/EventProcessingService.php
index 7564be8..263a917 100644
--- a/src/Service/EventProcessingService.php
+++ b/src/Service/EventProcessingService.php
@@ -7,7 +7,6 @@
 namespace Emico\RobinHqLib\Service;
 
 
-use Emico\RobinHqLib\Client\RobinClient;
 use Emico\RobinHqLib\Event\EventInterface;
 use Emico\RobinHqLib\EventProcessor\EventProcessorInterface;
 use Emico\RobinHqLib\Queue\Serializer\EventSerializer;
@@ -75,4 +74,4 @@ public function getEventSerializer(): EventSerializer
         }
         return $this->eventSerializer;
     }
-}
\ No newline at end of file
+}
diff --git a/src/Service/OrderService.php b/src/Service/OrderService.php
index 0813d9b..23a159c 100644
--- a/src/Service/OrderService.php
+++ b/src/Service/OrderService.php
@@ -14,17 +14,13 @@
 
 class OrderService
 {
-    private EventSerializer $eventSerializer;
-
     /**
      * CustomerService constructor.
-     * @param QueueInterface $queue
      */
-    public function __construct(private QueueInterface $queue)
-    {
-        $this->queue = $queue;
-        $this->eventSerializer = new EventSerializer();
-    }
+    public function __construct(
+        private QueueInterface $queue,
+        private EventSerializer $eventSerializer,
+    ) {}
 
     /**
      * @param Order $order
@@ -34,4 +30,4 @@ public function postOrder(Order $order): void
         $event = new OrderEvent($order);
         $this->queue->pushEvent($this->eventSerializer->serializeEvent($event));
     }
-}
\ No newline at end of file
+}