diff --git a/ConsumedMessageStats.php b/ConsumedMessageStats.php
index 928bce0..077ceeb 100644
--- a/ConsumedMessageStats.php
+++ b/ConsumedMessageStats.php
@@ -6,10 +6,10 @@
 
 class ConsumedMessageStats implements Stats
 {
-    const STATUS_ACK = 'acknowledged';
-    const STATUS_REJECTED = 'rejected';
-    const STATUS_REQUEUED = 'requeued';
-    const STATUS_FAILED = 'failed';
+    public const STATUS_ACK = 'acknowledged';
+    public const STATUS_REJECTED = 'rejected';
+    public const STATUS_REQUEUED = 'requeued';
+    public const STATUS_FAILED = 'failed';
 
     /**
      * @var string
@@ -102,12 +102,12 @@ public function __construct(
         array $properties,
         bool $redelivered,
         string $status,
-        string $errorClass = null,
-        string $errorMessage = null,
-        int $errorCode = null,
-        string $errorFile = null,
-        int $errorLine = null,
-        string $trace = null
+        ?string $errorClass = null,
+        ?string $errorMessage = null,
+        ?int $errorCode = null,
+        ?string $errorFile = null,
+        ?int $errorLine = null,
+        ?string $trace = null,
     ) {
         $this->consumerId = $consumerId;
         $this->timestampMs = $timestampMs;
diff --git a/ConsumerStats.php b/ConsumerStats.php
index d1a745d..d281b53 100644
--- a/ConsumerStats.php
+++ b/ConsumerStats.php
@@ -121,12 +121,12 @@ public function __construct(
         int $requeued,
         int $memoryUsage,
         float $systemLoad,
-        string $errorClass = null,
-        string $errorMessage = null,
-        int $errorCode = null,
-        string $errorFile = null,
-        int $errorLine = null,
-        string $trace = null
+        ?string $errorClass = null,
+        ?string $errorMessage = null,
+        ?int $errorCode = null,
+        ?string $errorFile = null,
+        ?int $errorLine = null,
+        ?string $trace = null,
     ) {
         $this->consumerId = $consumerId;
         $this->timestampMs = $timestampMs;
diff --git a/DatadogStorage.php b/DatadogStorage.php
index 82e841a..c10cbc6 100644
--- a/DatadogStorage.php
+++ b/DatadogStorage.php
@@ -30,7 +30,7 @@ public function __construct($config = 'datadog:')
         $this->config = $this->prepareConfig($config);
 
         if (null === $this->datadog) {
-            if (true === filter_var($this->config['batched'], FILTER_VALIDATE_BOOLEAN)) {
+            if (true === filter_var($this->config['batched'], \FILTER_VALIDATE_BOOLEAN)) {
                 $this->datadog = new BatchedDogStatsd($this->config);
             } else {
                 $this->datadog = new DogStatsd($this->config);
@@ -104,10 +104,7 @@ private function parseDsn(string $dsn): array
         $dsn = Dsn::parseFirst($dsn);
 
         if ('datadog' !== $dsn->getSchemeProtocol()) {
-            throw new \LogicException(sprintf(
-                'The given scheme protocol "%s" is not supported. It must be "datadog"',
-                $dsn->getSchemeProtocol()
-            ));
+            throw new \LogicException(sprintf('The given scheme protocol "%s" is not supported. It must be "datadog"', $dsn->getSchemeProtocol()));
         }
 
         return array_filter(array_replace($dsn->getQuery(), [
@@ -132,11 +129,6 @@ private function parseDsn(string $dsn): array
         });
     }
 
-    /**
-     * @param $config
-     *
-     * @return array
-     */
     private function prepareConfig($config): array
     {
         if (empty($config)) {
diff --git a/InfluxDbStorage.php b/InfluxDbStorage.php
index ff5f6c3..3084864 100644
--- a/InfluxDbStorage.php
+++ b/InfluxDbStorage.php
@@ -67,9 +67,9 @@ public function __construct($config = 'influxdb:')
             // and causes library to use defaults.
             @trigger_error(
                 sprintf('Passing %s as %s argument is deprecated. Pass it as "client" array property or use createWithClient instead',
-                Client::class,
-                __METHOD__
-            ), E_USER_DEPRECATED);
+                    Client::class,
+                    __METHOD__
+                ), \E_USER_DEPRECATED);
             $this->client = $config;
             $config = [];
         } else {
@@ -91,12 +91,7 @@ public function __construct($config = 'influxdb:')
 
         if (null !== $config['client']) {
             if (!$config['client'] instanceof Client) {
-                throw new \InvalidArgumentException(sprintf(
-                    '%s configuration property is expected to be an instance of %s class. %s was passed instead.',
-                    'client',
-                    Client::class,
-                    gettype($config['client'])
-                ));
+                throw new \InvalidArgumentException(sprintf('%s configuration property is expected to be an instance of %s class. %s was passed instead.', 'client', Client::class, gettype($config['client'])));
             }
             $this->client = $config['client'];
         }
@@ -105,10 +100,7 @@ public function __construct($config = 'influxdb:')
     }
 
     /**
-     * @param Client $client
      * @param string $config
-     *
-     * @return InfluxDbStorage
      */
     public static function createWithClient(Client $client, $config = 'influxdb:'): self
     {
@@ -254,10 +246,7 @@ private static function parseDsn(string $dsn): array
         $dsn = Dsn::parseFirst($dsn);
 
         if (false === in_array($dsn->getSchemeProtocol(), ['influxdb'], true)) {
-            throw new \LogicException(sprintf(
-                'The given scheme protocol "%s" is not supported. It must be "influxdb"',
-                $dsn->getSchemeProtocol()
-            ));
+            throw new \LogicException(sprintf('The given scheme protocol "%s" is not supported. It must be "influxdb"', $dsn->getSchemeProtocol()));
         }
 
         return array_filter(array_replace($dsn->getQuery(), [
diff --git a/JsonSerializer.php b/JsonSerializer.php
index 1edb60e..8d04609 100644
--- a/JsonSerializer.php
+++ b/JsonSerializer.php
@@ -22,12 +22,8 @@ public function toString(Stats $stats): string
 
         $json = json_encode($data);
 
-        if (JSON_ERROR_NONE !== json_last_error()) {
-            throw new \InvalidArgumentException(sprintf(
-                'The malformed json given. Error %s and message %s',
-                json_last_error(),
-                json_last_error_msg()
-            ));
+        if (\JSON_ERROR_NONE !== json_last_error()) {
+            throw new \InvalidArgumentException(sprintf('The malformed json given. Error %s and message %s', json_last_error(), json_last_error_msg()));
         }
 
         return $json;
diff --git a/Resources.php b/Resources.php
index 2a5995f..409d986 100644
--- a/Resources.php
+++ b/Resources.php
@@ -7,7 +7,7 @@ final class Resources
     /**
      * @var array
      */
-    private static $knownStorages = null;
+    private static $knownStorages;
 
     private function __construct()
     {
diff --git a/SentMessageStats.php b/SentMessageStats.php
index 6106d3d..f8ddc73 100644
--- a/SentMessageStats.php
+++ b/SentMessageStats.php
@@ -48,7 +48,7 @@ public function __construct(
         ?string $messageId,
         ?string $correlationId,
         array $headers,
-        array $properties
+        array $properties,
     ) {
         $this->timestampMs = $timestampMs;
         $this->destination = $destination;
diff --git a/WampStorage.php b/WampStorage.php
index 44623d4..0d5ba18 100644
--- a/WampStorage.php
+++ b/WampStorage.php
@@ -195,10 +195,7 @@ private function parseDsn(string $dsn): array
         $dsn = Dsn::parseFirst($dsn);
 
         if (false === in_array($dsn->getSchemeProtocol(), ['wamp', 'ws'], true)) {
-            throw new \LogicException(sprintf(
-                'The given scheme protocol "%s" is not supported. It must be "wamp"',
-                $dsn->getSchemeProtocol()
-            ));
+            throw new \LogicException(sprintf('The given scheme protocol "%s" is not supported. It must be "wamp"', $dsn->getSchemeProtocol()));
         }
 
         return array_filter(array_replace($dsn->getQuery(), [