diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index fd322b8b..cc762523 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -25,6 +25,7 @@ jobs:
           - "8.2"
           - "8.3"
           - "8.4"
+          - "8.5"
         dependencies:
           - "highest"
         include:
@@ -33,7 +34,7 @@ jobs:
 
     steps:
       - name: "Checkout"
-        uses: "actions/checkout@v4"
+        uses: "actions/checkout@v6"
         with:
           fetch-depth: 2
 
@@ -45,7 +46,7 @@ jobs:
           ini-values: "zend.assertions=1"
 
       - name: "Install dependencies with Composer"
-        uses: "ramsey/composer-install@v3"
+        uses: "ramsey/composer-install@v4"
         with:
           dependency-versions: "${{ matrix.dependencies }}"
 
diff --git a/src/Ratchet/Server/FlashPolicy.php b/src/Ratchet/Server/FlashPolicy.php
index 4a1b8bdf..c8636ae8 100644
--- a/src/Ratchet/Server/FlashPolicy.php
+++ b/src/Ratchet/Server/FlashPolicy.php
@@ -66,7 +66,7 @@ public function addAllowedAccess($domain, $ports = '*', $secure = false) {
            throw new \UnexpectedValueException('Invalid Port');
         }
 
-        $this->_access[]   = array($domain, $ports, (boolean)$secure);
+        $this->_access[]   = array($domain, $ports, (bool)$secure);
         $this->_cacheValid = false;
 
         return $this;
diff --git a/src/Ratchet/Wamp/ServerProtocol.php b/src/Ratchet/Wamp/ServerProtocol.php
index 2d6d799c..781a5964 100644
--- a/src/Ratchet/Wamp/ServerProtocol.php
+++ b/src/Ratchet/Wamp/ServerProtocol.php
@@ -72,7 +72,7 @@ public function getSubProtocols() {
      */
     public function onOpen(ConnectionInterface $conn) {
         $decor = new WampConnection($conn);
-        $this->connections->attach($conn, $decor);
+        $this->connections->offsetSet($conn, $decor);
 
         $this->_decorating->onOpen($decor);
     }
@@ -125,7 +125,7 @@ public function onMessage(ConnectionInterface $from, $msg) {
             case static::MSG_PUBLISH:
                 $exclude  = (array_key_exists(3, $json) ? $json[3] : null);
                 if (!is_array($exclude)) {
-                    if (true === (boolean)$exclude) {
+                    if (true === (bool)$exclude) {
                         $exclude = [$from->WAMP->sessionId];
                     } else {
                         $exclude = [];
@@ -147,7 +147,7 @@ public function onMessage(ConnectionInterface $from, $msg) {
      */
     public function onClose(ConnectionInterface $conn) {
         $decor = $this->connections[$conn];
-        $this->connections->detach($conn);
+        $this->connections->offsetUnset($conn);
 
         $this->_decorating->onClose($decor);
     }
diff --git a/src/Ratchet/Wamp/Topic.php b/src/Ratchet/Wamp/Topic.php
index 675b236e..a1a0580c 100644
--- a/src/Ratchet/Wamp/Topic.php
+++ b/src/Ratchet/Wamp/Topic.php
@@ -58,7 +58,7 @@ public function broadcast($msg, array $exclude = array(), array $eligible = arra
      * @return boolean
      */
     public function has(ConnectionInterface $conn) {
-        return $this->subscribers->contains($conn);
+        return $this->subscribers->offsetExists($conn);
     }
 
     /**
@@ -66,7 +66,7 @@ public function has(ConnectionInterface $conn) {
      * @return Topic
      */
     public function add(ConnectionInterface $conn) {
-        $this->subscribers->attach($conn);
+        $this->subscribers->offsetSet($conn);
 
         return $this;
     }
@@ -76,8 +76,8 @@ public function add(ConnectionInterface $conn) {
      * @return Topic
      */
     public function remove(ConnectionInterface $conn) {
-        if ($this->subscribers->contains($conn)) {
-            $this->subscribers->detach($conn);
+        if ($this->subscribers->offsetExists($conn)) {
+            $this->subscribers->offsetUnset($conn);
         }
 
         return $this;
diff --git a/src/Ratchet/Wamp/TopicManager.php b/src/Ratchet/Wamp/TopicManager.php
index dd06ada4..e2b2936c 100644
--- a/src/Ratchet/Wamp/TopicManager.php
+++ b/src/Ratchet/Wamp/TopicManager.php
@@ -39,12 +39,12 @@ public function onCall(ConnectionInterface $conn, $id, $topic, array $params) {
     public function onSubscribe(ConnectionInterface $conn, $topic) {
         $topicObj = $this->getTopic($topic);
 
-        if ($conn->WAMP->subscriptions->contains($topicObj)) {
+        if ($conn->WAMP->subscriptions->offsetExists($topicObj)) {
             return;
         }
 
         $this->topicLookup[$topic]->add($conn);
-        $conn->WAMP->subscriptions->attach($topicObj);
+        $conn->WAMP->subscriptions->offsetSet($topicObj);
         $this->app->onSubscribe($conn, $topicObj);
     }
 
@@ -54,7 +54,7 @@ public function onSubscribe(ConnectionInterface $conn, $topic) {
     public function onUnsubscribe(ConnectionInterface $conn, $topic) {
         $topicObj = $this->getTopic($topic);
 
-        if (!$conn->WAMP->subscriptions->contains($topicObj)) {
+        if (!$conn->WAMP->subscriptions->offsetExists($topicObj)) {
             return;
         }
 
@@ -112,8 +112,8 @@ protected function getTopic($topic) {
     }
 
     protected function cleanTopic(Topic $topic, ConnectionInterface $conn) {
-        if ($conn->WAMP->subscriptions->contains($topic)) {
-            $conn->WAMP->subscriptions->detach($topic);
+        if ($conn->WAMP->subscriptions->offsetExists($topic)) {
+            $conn->WAMP->subscriptions->offsetUnset($topic);
         }
 
         $this->topicLookup[$topic->getId()]->remove($conn);
diff --git a/src/Ratchet/WebSocket/WsServer.php b/src/Ratchet/WebSocket/WsServer.php
index 88c56348..67218fe8 100644
--- a/src/Ratchet/WebSocket/WsServer.php
+++ b/src/Ratchet/WebSocket/WsServer.php
@@ -150,7 +150,7 @@ function(FrameInterface $frame) use ($wsConn) {
             $this->ueFlowFactory
         );
 
-        $this->connections->attach($conn, new ConnContext($wsConn, $streamer));
+        $this->connections->offsetSet($conn, new ConnContext($wsConn, $streamer));
 
         return $this->delegate->onOpen($wsConn);
     }
@@ -170,9 +170,9 @@ public function onMessage(ConnectionInterface $from, $msg) {
      * {@inheritdoc}
      */
     public function onClose(ConnectionInterface $conn) {
-        if ($this->connections->contains($conn)) {
+        if ($this->connections->offsetExists($conn)) {
             $context = $this->connections[$conn];
-            $this->connections->detach($conn);
+            $this->connections->offsetUnset($conn);
 
             $this->delegate->onClose($context->connection);
         }
@@ -182,7 +182,7 @@ public function onClose(ConnectionInterface $conn) {
      * {@inheritdoc}
      */
     public function onError(ConnectionInterface $conn, \Exception $e) {
-        if ($this->connections->contains($conn)) {
+        if ($this->connections->offsetExists($conn)) {
             $this->delegate->onError($this->connections[$conn]->connection, $e);
         } else {
             $conn->close();
@@ -215,7 +215,7 @@ public function enableKeepAlive(LoopInterface $loop, $interval = 30) {
 
         $this->pongReceiver = function(FrameInterface $frame, $wsConn) use ($pingedConnections, &$lastPing) {
             if ($frame->getPayload() === $lastPing->getPayload()) {
-                $pingedConnections->detach($wsConn);
+                $pingedConnections->offsetUnset($wsConn);
             }
         };
 
@@ -231,7 +231,7 @@ public function enableKeepAlive(LoopInterface $loop, $interval = 30) {
                 $wsConn  = $this->connections[$conn]->connection;
 
                 $wsConn->send($lastPing);
-                $pingedConnections->attach($wsConn);
+                $pingedConnections->offsetSet($wsConn);
             }
         });
    }
diff --git a/tests/unit/AbstractConnectionDecoratorTest.php b/tests/unit/AbstractConnectionDecoratorTest.php
index 8c5b379c..b3fff560 100644
--- a/tests/unit/AbstractConnectionDecoratorTest.php
+++ b/tests/unit/AbstractConnectionDecoratorTest.php
@@ -90,7 +90,9 @@ public function testUnsetLevel2() {
     public function testGetConnection() {
         $class  = new \ReflectionClass('Ratchet\\AbstractConnectionDecorator');
         $method = $class->getMethod('getConnection');
-        $method->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $method->setAccessible(true);
+        }
 
         $conn = $method->invokeArgs($this->l1, array());
 
@@ -100,7 +102,9 @@ public function testGetConnection() {
     public function testGetConnectionLevel2() {
         $class  = new \ReflectionClass('Ratchet\\AbstractConnectionDecorator');
         $method = $class->getMethod('getConnection');
-        $method->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $method->setAccessible(true);
+        }
 
         $conn = $method->invokeArgs($this->l2, array());
 
diff --git a/tests/unit/AppTest.php b/tests/unit/AppTest.php
index b3c879e3..645ccf80 100644
--- a/tests/unit/AppTest.php
+++ b/tests/unit/AppTest.php
@@ -23,7 +23,9 @@ public function testCtorWithoutArgumentsStartsListeningOnDefaultPorts() {
         $app = new App();
 
         $ref = new \ReflectionProperty($app, '_server');
-        $ref->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $server = $ref->getValue($app);
         assert($server instanceof IoServer);
 
diff --git a/tests/unit/Session/SessionProviderTest.php b/tests/unit/Session/SessionProviderTest.php
index 2bec51b0..7100db24 100644
--- a/tests/unit/Session/SessionProviderTest.php
+++ b/tests/unit/Session/SessionProviderTest.php
@@ -66,7 +66,9 @@ public function classCaseProvider() {
     public function testToClassCase($in, $out) {
         $ref = new \ReflectionClass('Ratchet\\Session\\SessionProvider');
         $method = $ref->getMethod('toClassCase');
-        $method->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $method->setAccessible(true);
+        }
 
         $component = new SessionProvider($this->getMockBuilder($this->getComponentClassString())->getMock(), $this->getMockBuilder('SessionHandlerInterface')->getMock());
         $this->assertEquals($out, $method->invokeArgs($component, array($in)));
diff --git a/tests/unit/Wamp/ServerProtocolTest.php b/tests/unit/Wamp/ServerProtocolTest.php
index 4e4983fa..9d4bdd89 100644
--- a/tests/unit/Wamp/ServerProtocolTest.php
+++ b/tests/unit/Wamp/ServerProtocolTest.php
@@ -190,7 +190,9 @@ public function testOnClosePropagation() {
 
         $class  = new \ReflectionClass('Ratchet\\Wamp\\WampConnection');
         $method = $class->getMethod('getConnection');
-        $method->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $method->setAccessible(true);
+        }
 
         $check = $method->invokeArgs($this->_app->last['onClose'][0], array());
 
@@ -207,7 +209,9 @@ public function testOnErrorPropagation() {
 
         $class  = new \ReflectionClass('Ratchet\\Wamp\\WampConnection');
         $method = $class->getMethod('getConnection');
-        $method->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $method->setAccessible(true);
+        }
 
         $check = $method->invokeArgs($this->_app->last['onError'][0], array());
 
diff --git a/tests/unit/Wamp/TopicManagerTest.php b/tests/unit/Wamp/TopicManagerTest.php
index fd67fdd5..bd6c0149 100644
--- a/tests/unit/Wamp/TopicManagerTest.php
+++ b/tests/unit/Wamp/TopicManagerTest.php
@@ -34,7 +34,9 @@ public function setUpManager() {
     public function testGetTopicReturnsTopicObject() {
         $class  = new \ReflectionClass('Ratchet\Wamp\TopicManager');
         $method = $class->getMethod('getTopic');
-        $method->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $method->setAccessible(true);
+        }
 
         $topic = $method->invokeArgs($this->mngr, array('The Topic'));
 
@@ -46,7 +48,9 @@ public function testGetTopicCreatesTopicWithSameName() {
 
         $class  = new \ReflectionClass('Ratchet\Wamp\TopicManager');
         $method = $class->getMethod('getTopic');
-        $method->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $method->setAccessible(true);
+        }
 
         $topic = $method->invokeArgs($this->mngr, array($name));
 
@@ -56,7 +60,9 @@ public function testGetTopicCreatesTopicWithSameName() {
     public function testGetTopicReturnsSameObject() {
         $class  = new \ReflectionClass('Ratchet\Wamp\TopicManager');
         $method = $class->getMethod('getTopic');
-        $method->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $method->setAccessible(true);
+        }
 
         $topic = $method->invokeArgs($this->mngr, array('No copy'));
         $again = $method->invokeArgs($this->mngr, array('No copy'));
@@ -95,13 +101,15 @@ public function testTopicIsInConnectionOnSubscribe() {
 
         $class  = new \ReflectionClass('Ratchet\Wamp\TopicManager');
         $method = $class->getMethod('getTopic');
-        $method->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $method->setAccessible(true);
+        }
 
         $topic = $method->invokeArgs($this->mngr, array($name));
 
         $this->mngr->onSubscribe($this->conn, $name);
 
-        $this->assertTrue($this->conn->WAMP->subscriptions->contains($topic));
+        $this->assertTrue($this->conn->WAMP->subscriptions->offsetExists($topic));
     }
 
     public function testDoubleSubscriptionFiresOnce() {
@@ -135,14 +143,16 @@ public function testUnsubscribeRemovesTopicFromConnection() {
 
         $class  = new \ReflectionClass('Ratchet\Wamp\TopicManager');
         $method = $class->getMethod('getTopic');
-        $method->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $method->setAccessible(true);
+        }
 
         $topic = $method->invokeArgs($this->mngr, array($name));
 
         $this->mngr->onSubscribe($this->conn, $name);
         $this->mngr->onUnsubscribe($this->conn, $name);
 
-        $this->assertFalse($this->conn->WAMP->subscriptions->contains($topic));
+        $this->assertFalse($this->conn->WAMP->subscriptions->offsetExists($topic));
     }
 
     public function testOnPublishBubbles() {
@@ -167,10 +177,14 @@ public function testOnCloseBubbles() {
     protected function topicProvider($name) {
         $class  = new \ReflectionClass('Ratchet\Wamp\TopicManager');
         $method = $class->getMethod('getTopic');
-        $method->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $method->setAccessible(true);
+        }
 
         $attribute = $class->getProperty('topicLookup');
-        $attribute->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $attribute->setAccessible(true);
+        }
 
         $topic = $method->invokeArgs($this->mngr, array($name));