diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index fed4af2d..42049106 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -31,6 +31,8 @@ jobs:
           - '8.1'
           - '8.2'
           - '8.3'
+          - '8.4'
+          - '8.5'
     steps:
       - name: Checkout code
         uses: actions/checkout@v3
@@ -60,7 +62,7 @@ jobs:
 
       - name: SonarQube Scan (Push)
         if: matrix.version == '8.2' && github.event_name == 'push'
-        uses: SonarSource/sonarcloud-github-action@v1.9
+        uses: SonarSource/sonarcloud-github-action@v3
         env:
           SONAR_TOKEN: ${{ secrets.SONARQUBE_TOKEN }}
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
@@ -72,7 +74,7 @@ jobs:
 
       - name: SonarQube Scan (Pull Request)
         if: matrix.version == '8.2' && github.event_name == 'pull_request'
-        uses: SonarSource/sonarcloud-github-action@v1.9
+        uses: SonarSource/sonarcloud-github-action@v3
         env:
           SONAR_TOKEN: ${{ secrets.SONARQUBE_TOKEN }}
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/README.md b/README.md
index daa54d57..701b5dce 100644
--- a/README.md
+++ b/README.md
@@ -8,7 +8,7 @@
 This SDK is designed to work with Split, the platform for controlled rollouts, which serves features to your users via feature flags to manage your complete customer experience.
 
 ## Compatibility
-This SDK is compatible with PHP 7.3 and above.
+This SDK is compatible with PHP 7.3 and above, including PHP 8.4 and 8.5.
 
 ## Getting started
 Below is a simple example that describes the instantiation and most basic usage of our SDK.
diff --git a/src/SplitIO/Component/Log/Logger.php b/src/SplitIO/Component/Log/Logger.php
index d05dddb1..1c0735d9 100644
--- a/src/SplitIO/Component/Log/Logger.php
+++ b/src/SplitIO/Component/Log/Logger.php
@@ -38,7 +38,7 @@ class Logger extends LoggerTrait
      * Logger constructor
      * @param LogHandlerInterface|null $handler
      */
-    public function __construct(LogHandlerInterface $handler = null, $level = LogLevel::WARNING)
+    public function __construct(?LogHandlerInterface $handler = null, $level = LogLevel::WARNING)
     {
         $this->logLevel = $this->logLevels[$level];
 
diff --git a/src/SplitIO/Engine.php b/src/SplitIO/Engine.php
index d539fe8c..f4cd9b28 100644
--- a/src/SplitIO/Engine.php
+++ b/src/SplitIO/Engine.php
@@ -21,7 +21,7 @@ class Engine
      * @param array|null $attributes
      * @return array
      */
-    public static function getTreatment($matchingKey, $bucketingKey, SplitGrammar $split, array $attributes = null)
+    public static function getTreatment($matchingKey, $bucketingKey, SplitGrammar $split, ?array $attributes = null)
     {
         if ($bucketingKey === null) {
             $bucketingKey = $matchingKey;
diff --git a/src/SplitIO/Grammar/Condition.php b/src/SplitIO/Grammar/Condition.php
index 7266c5e3..3d40083f 100644
--- a/src/SplitIO/Grammar/Condition.php
+++ b/src/SplitIO/Grammar/Condition.php
@@ -68,7 +68,7 @@ public function __construct(array $condition)
      * @param array|null $attributes
      * @return bool
      */
-    public function match($key, array $attributes = null, $bucketingKey = null)
+    public function match($key, ?array $attributes = null, $bucketingKey = null)
     {
         $eval = array();
         foreach ($this->matcherGroup as $matcher) {
diff --git a/src/SplitIO/Sdk/Client.php b/src/SplitIO/Sdk/Client.php
index 0b7e2dd5..e21432d4 100644
--- a/src/SplitIO/Sdk/Client.php
+++ b/src/SplitIO/Sdk/Client.php
@@ -74,7 +74,7 @@ private function createImpression($key, $featureFlag, $treatment, $changeNumber,
      *
      * @return null|mixed
      */
-    private function doInputValidationForTreatment($key, $featureFlagName, array $attributes = null, $operation)
+    private function doInputValidationForTreatment($key, $featureFlagName, $operation, ?array $attributes = null)
     {
         $key = InputValidator::validateKey($key, $operation);
         if (is_null($key)) {
@@ -112,7 +112,7 @@ private function doEvaluation($operation, $key, $featureFlagName, $attributes)
     {
         $default = array('treatment' => TreatmentEnum::CONTROL, 'config' => null);
 
-        $inputValidation = $this->doInputValidationForTreatment($key, $featureFlagName, $attributes, $operation);
+        $inputValidation = $this->doInputValidationForTreatment($key, $featureFlagName, $operation, $attributes);
         if (is_null($inputValidation)) {
             return $default;
         }
@@ -169,7 +169,7 @@ private function doEvaluation($operation, $key, $featureFlagName, $attributes)
     /**
      * @inheritdoc
      */
-    public function getTreatment($key, $featureName, array $attributes = null)
+    public function getTreatment($key, $featureName, ?array $attributes = null)
     {
         try {
             $result = $this->doEvaluation(
@@ -188,7 +188,7 @@ public function getTreatment($key, $featureName, array $attributes = null)
     /**
      * @inheritdoc
      */
-    public function getTreatmentWithConfig($key, $featureFlagName, array $attributes = null)
+    public function getTreatmentWithConfig($key, $featureFlagName, ?array $attributes = null)
     {
         try {
             return $this->doEvaluation(
@@ -213,7 +213,7 @@ public function getTreatmentWithConfig($key, $featureFlagName, array $attributes
      *
      * @return null|mixed
      */
-    private function doInputValidationForTreatments($key, $featureFlagNames, array $attributes = null, $operation)
+    private function doInputValidationForTreatments($key, $featureFlagNames, $operation, ?array $attributes = null)
     {
         $featureFlags = InputValidator::validateFeatureFlagNames($featureFlagNames, $operation);
         if (is_null($featureFlags)) {
@@ -264,7 +264,7 @@ private function registerData($impressions, $attributes)
      */
     private function doEvaluationForTreatments($operation, $key, $featureFlagNames, $attributes)
     {
-        $inputValidation = $this->doInputValidationForTreatments($key, $featureFlagNames, $attributes, $operation);
+        $inputValidation = $this->doInputValidationForTreatments($key, $featureFlagNames, $operation, $attributes);
         if (is_null($inputValidation)) {
             return array();
         }
@@ -301,7 +301,7 @@ private function doEvaluationForTreatments($operation, $key, $featureFlagNames,
     /**
      * @inheritdoc
      */
-    public function getTreatments($key, $featureFlagNames, array $attributes = null)
+    public function getTreatments($key, $featureFlagNames, ?array $attributes = null)
     {
         try {
             return array_map(
@@ -325,7 +325,7 @@ function ($feature) {
     /**
      * @inheritdoc
      */
-    public function getTreatmentsWithConfig($key, $featureFlagNames, array $attributes = null)
+    public function getTreatmentsWithConfig($key, $featureFlagNames, ?array $attributes = null)
     {
         try {
             return $this->doEvaluationForTreatments(
@@ -396,7 +396,7 @@ public function track($key, $trafficType, $eventType, $value = null, $properties
         return false;
     }
 
-    public function getTreatmentsByFlagSets($key, $flagSets, array $attributes = null)
+    public function getTreatmentsByFlagSets($key, $flagSets, ?array $attributes = null)
     {
         try {
             return array_map(
@@ -416,7 +416,7 @@ function ($feature) {
         }
     }
 
-    public function getTreatmentsWithConfigByFlagSets($key, $flagSets, array $attributes = null)
+    public function getTreatmentsWithConfigByFlagSets($key, $flagSets, ?array $attributes = null)
     {
         try {
             return $this->doEvaluationByFlagSets(
@@ -431,7 +431,7 @@ public function getTreatmentsWithConfigByFlagSets($key, $flagSets, array $attrib
         }
     }
 
-    public function getTreatmentsByFlagSet($key, $flagSet, array $attributes = null)
+    public function getTreatmentsByFlagSet($key, $flagSet, ?array $attributes = null)
     {
         try {
             return array_map(
@@ -451,7 +451,7 @@ function ($feature) {
         }
     }
 
-    public function getTreatmentsWithConfigByFlagSet($key, $flagSet, array $attributes = null)
+    public function getTreatmentsWithConfigByFlagSet($key, $flagSet, ?array $attributes = null)
     {
         try {
             return $this->doEvaluationByFlagSets(
@@ -466,7 +466,7 @@ public function getTreatmentsWithConfigByFlagSet($key, $flagSet, array $attribut
         }
     }
 
-    private function doInputValidationByFlagSets($key, $flagSets, array $attributes = null, $operation)
+    private function doInputValidationByFlagSets($key, $flagSets, $operation, ?array $attributes = null)
     {
         $key = InputValidator::validateKey($key, $operation);
         if (is_null($key) || !InputValidator::validAttributes($attributes, $operation)) {
@@ -487,7 +487,7 @@ private function doInputValidationByFlagSets($key, $flagSets, array $attributes
 
     private function doEvaluationByFlagSets($operation, $key, $flagSets, $attributes)
     {
-        $inputValidation = $this->doInputValidationByFlagSets($key, $flagSets, $attributes, $operation);
+        $inputValidation = $this->doInputValidationByFlagSets($key, $flagSets, $operation, $attributes);
         if (is_null($inputValidation)) {
             return array();
         }
diff --git a/src/SplitIO/Sdk/ClientInterface.php b/src/SplitIO/Sdk/ClientInterface.php
index d661d143..36cb950b 100644
--- a/src/SplitIO/Sdk/ClientInterface.php
+++ b/src/SplitIO/Sdk/ClientInterface.php
@@ -36,7 +36,7 @@ interface ClientInterface
      * @param $attributes
      * @return string
      */
-    public function getTreatment($key, $featureFlagName, array $attributes = null);
+    public function getTreatment($key, $featureFlagName, ?array $attributes = null);
 
     /**
      * Returns an object with the treatment to show this id for this feature
@@ -76,7 +76,7 @@ public function getTreatment($key, $featureFlagName, array $attributes = null);
      * @param $attributes
      * @return array
      */
-    public function getTreatmentWithConfig($key, $featureFlagName, array $attributes = null);
+    public function getTreatmentWithConfig($key, $featureFlagName, ?array $attributes = null);
 
     /**
      * Returns an associative array which each key will be
@@ -109,7 +109,7 @@ public function getTreatmentWithConfig($key, $featureFlagName, array $attributes
      * @param $attributes
      * @return array
      */
-    public function getTreatments($key, $featureFlagNames, array $attributes = null);
+    public function getTreatments($key, $featureFlagNames, ?array $attributes = null);
 
     /**
      * Returns an associative array which each key will be
@@ -144,7 +144,7 @@ public function getTreatments($key, $featureFlagNames, array $attributes = null)
      * @param $attributes
      * @return array
      */
-    public function getTreatmentsWithConfig($key, $featureFlagNames, array $attributes = null);
+    public function getTreatmentsWithConfig($key, $featureFlagNames, ?array $attributes = null);
 
     /**
      * Returns an associative array which each key will be
@@ -172,7 +172,7 @@ public function getTreatmentsWithConfig($key, $featureFlagNames, array $attribut
      * @param $attributes
      * @return array
      */
-    public function getTreatmentsWithConfigByFlagSets($key, $flagSets, array $attributes = null);
+    public function getTreatmentsWithConfigByFlagSets($key, $flagSets, ?array $attributes = null);
 
     /**
      * Returns an associative array which each key will be
@@ -200,7 +200,7 @@ public function getTreatmentsWithConfigByFlagSets($key, $flagSets, array $attrib
      * @param $attributes
      * @return array
      */
-    public function getTreatmentsByFlagSets($key, $flagSets, array $attributes = null);
+    public function getTreatmentsByFlagSets($key, $flagSets, ?array $attributes = null);
 
     /**
      * Returns an associative array which each key will be
@@ -234,7 +234,7 @@ public function getTreatmentsByFlagSets($key, $flagSets, array $attributes = nul
      * @param $attributes
      * @return array
      */
-    public function getTreatmentsByFlagSet($key, $flagSet, array $attributes = null);
+    public function getTreatmentsByFlagSet($key, $flagSet, ?array $attributes = null);
     
     /**
      * Returns an associative array which each key will be
@@ -262,7 +262,7 @@ public function getTreatmentsByFlagSet($key, $flagSet, array $attributes = null)
      * @param $attributes
      * @return array
      */
-    public function getTreatmentsWithConfigByFlagSet($key, $flagSet, array $attributes = null);
+    public function getTreatmentsWithConfigByFlagSet($key, $flagSet, ?array $attributes = null);
 
     /**
      * A short-hand for
diff --git a/src/SplitIO/Sdk/Evaluator.php b/src/SplitIO/Sdk/Evaluator.php
index 5e754d6d..a403278d 100644
--- a/src/SplitIO/Sdk/Evaluator.php
+++ b/src/SplitIO/Sdk/Evaluator.php
@@ -63,7 +63,7 @@ private function fetchFeatureFlagNamesByFlagSets($flagSets)
         return array_values(array_unique($toReturn));
     }
 
-    public function evaluateFeature($matchingKey, $bucketingKey, $featureName, array $attributes = null)
+    public function evaluateFeature($matchingKey, $bucketingKey, $featureName, ?array $attributes = null)
     {
         $timeStart = Metrics::startMeasuringLatency();
         $split = $this->fetchSplit($featureName);
@@ -72,7 +72,7 @@ public function evaluateFeature($matchingKey, $bucketingKey, $featureName, array
         return $toReturn;
     }
 
-    public function evaluateFeatures($matchingKey, $bucketingKey, array $featureNames, array $attributes = null)
+    public function evaluateFeatures($matchingKey, $bucketingKey, array $featureNames, ?array $attributes = null)
     {
         $toReturn = array(
             'evaluations' => array(),
@@ -86,7 +86,7 @@ public function evaluateFeatures($matchingKey, $bucketingKey, array $featureName
         return $toReturn;
     }
 
-    public function evaluateFeaturesByFlagSets($matchingKey, $bucketingKey, array $flagSets, array $attributes = null)
+    public function evaluateFeaturesByFlagSets($matchingKey, $bucketingKey, array $flagSets, ?array $attributes = null)
     {
         $timeStart = Metrics::startMeasuringLatency();
         $featureFlagNames = $this->fetchFeatureFlagNamesByFlagSets($flagSets);
@@ -95,7 +95,7 @@ public function evaluateFeaturesByFlagSets($matchingKey, $bucketingKey, array $f
         return $toReturn;
     }
 
-    private function evalTreatment($key, $bucketingKey, $split, array $attributes = null)
+    private function evalTreatment($key, $bucketingKey, $split, ?array $attributes = null)
     {
         $result = array(
             'treatment' => TreatmentEnum::CONTROL,
diff --git a/src/SplitIO/Sdk/LocalhostClient.php b/src/SplitIO/Sdk/LocalhostClient.php
index b9e13a83..d0ac56fe 100644
--- a/src/SplitIO/Sdk/LocalhostClient.php
+++ b/src/SplitIO/Sdk/LocalhostClient.php
@@ -136,7 +136,7 @@ public function doValidation($key, $featureFlagName, $operation)
     /**
      * @inheritdoc
      */
-    public function getTreatment($key, $featureFlagName, array $attributes = null)
+    public function getTreatment($key, $featureFlagName, ?array $attributes = null)
     {
         $key = $this->doValidation($key, $featureFlagName, "getTreatment");
         if (is_null($key)) {
@@ -157,7 +157,7 @@ public function getTreatment($key, $featureFlagName, array $attributes = null)
     /**
      * @inheritdoc
      */
-    public function getTreatmentWithConfig($key, $featureFlagName, array $attributes = null)
+    public function getTreatmentWithConfig($key, $featureFlagName, ?array $attributes = null)
     {
         $treatmentResult = array(
             "treatment" => TreatmentEnum::CONTROL,
@@ -189,7 +189,7 @@ public function getTreatmentWithConfig($key, $featureFlagName, array $attributes
     /**
      * @inheritdoc
      */
-    public function getTreatments($key, $featureFlagNames, array $attributes = null)
+    public function getTreatments($key, $featureFlagNames, ?array $attributes = null)
     {
         $result = array();
 
@@ -213,7 +213,7 @@ public function getTreatments($key, $featureFlagNames, array $attributes = null)
     /**
      * @inheritdoc
      */
-    public function getTreatmentsWithConfig($key, $featureFlagNames, array $attributes = null)
+    public function getTreatmentsWithConfig($key, $featureFlagNames, ?array $attributes = null)
     {
         $result = array();
 
@@ -258,25 +258,25 @@ public function track($key, $trafficType, $eventType, $value = null)
         return true;
     }
 
-    public function getTreatmentsWithConfigByFlagSets($key, $flagSets, array $attributes = null)
+    public function getTreatmentsWithConfigByFlagSets($key, $flagSets, ?array $attributes = null)
     {
         // no-op
         return array();
     }
     
-    public function getTreatmentsByFlagSets($key, $flagSets, array $attributes = null)
+    public function getTreatmentsByFlagSets($key, $flagSets, ?array $attributes = null)
     {
         // no-op
         return array();
     }
 
-    public function getTreatmentsWithConfigByFlagSet($key, $flagSet, array $attributes = null)
+    public function getTreatmentsWithConfigByFlagSet($key, $flagSet, ?array $attributes = null)
     {
         // no-op
         return array();
     }
     
-    public function getTreatmentsByFlagSet($key, $flagSet, array $attributes = null)
+    public function getTreatmentsByFlagSet($key, $flagSet, ?array $attributes = null)
     {
         // no-op
         return array();