diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b7886d1e..e583db4e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,7 +9,7 @@ jobs:
     strategy:
       matrix:
         operating-system: ['ubuntu-latest']
-        php-versions: ['5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0']
+        php-versions: ['7.2', '7.3', '7.4', '8.0', '8.1']
         phpunit-versions: ['latest']
     steps:
       - name: Checkout
diff --git a/.gitignore b/.gitignore
index 8fc16d75..498d6c99 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 composer.lock
 phpunit.xml
 .phpunit
+.phpunit.*
 vendor
 .php_cs.cache
 .php_cs
diff --git a/Command/MongoDBMigrateMetadataCommand.php b/Command/MongoDBMigrateMetadataCommand.php
index 3bd6689d..d5e399cf 100644
--- a/Command/MongoDBMigrateMetadataCommand.php
+++ b/Command/MongoDBMigrateMetadataCommand.php
@@ -66,7 +66,7 @@ protected function configure()
 fields to a new schema optimized for MongoDB queries. This command requires the
 participant class to be provided as its first and only parameter:
 
-  <info>php app/console fos:message:mongodb:migrate:metadata "Acme\Document\User"</info>
+  <info>php bin/console fos:message:mongodb:migrate:metadata "Acme\Document\User"</info>
 
 The following hash fields will become obsolete after migration:
 
@@ -104,15 +104,15 @@ protected function initialize(InputInterface $input, OutputInterface $output)
         $this->threadCollection = $this->getMongoCollectionForClass($registry, $this->getContainer()->getParameter('fos_message.thread_class'));
         $this->participantCollection = $this->getMongoCollectionForClass($registry, $input->getArgument('participantClass'));
 
-        $this->updateOptions = array(
+        $this->updateOptions = [
             'multiple' => false,
             'safe' => $input->getOption('safe'),
-            'fsync' => $input->getOption('fsync'),
-        );
+            'fsync' => $input->getOption('fsync')
+        ];
 
         $this->printStatusCallback = function () {
         };
-        register_tick_function(array($this, 'printStatus'));
+        register_tick_function([$this, 'printStatus']);
     }
 
     /**
@@ -124,7 +124,7 @@ protected function execute(InputInterface $input, OutputInterface $output)
         $this->migrateThreads($output);
 
         $size = memory_get_peak_usage(true);
-        $unit = array('b', 'k', 'm', 'g', 't', 'p');
+        $unit = ['b', 'k', 'm', 'g', 't', 'p'];
         $output->writeln(sprintf('Peak Memory Usage: <comment>%s</comment>', round($size / pow(1024, $i = floor(log($size, 1024))), 2).$unit[$i]));
     }
 
@@ -134,11 +134,8 @@ protected function execute(InputInterface $input, OutputInterface $output)
     private function migrateMessages(OutputInterface $output)
     {
         $cursor = $this->messageCollection->find(
-            array('metadata' => array('$exists' => false)),
-            array(
-                'isReadByParticipant' => 1,
-                'isSpam' => 1,
-            )
+            ['metadata' => ['$exists' => false]],
+            ['isReadByParticipant' => 1, 'isSpam' => 1]
         );
         $cursor->snapshot();
 
@@ -160,11 +157,11 @@ private function migrateMessages(OutputInterface $output)
                 $this->createMessageUnreadForParticipants($message);
 
                 $this->messageCollection->update(
-                    array('_id' => $message['_id']),
-                    array('$set' => array(
+                    ['_id' => $message['_id']],
+                    ['$set' => [
                         'metadata' => $message['metadata'],
-                        'unreadForParticipants' => $message['unreadForParticipants'],
-                    )),
+                        'unreadForParticipants' => $message['unreadForParticipants']
+                    ]],
                     $this->updateOptions
                 );
                 ++$numProcessed;
@@ -181,15 +178,15 @@ private function migrateMessages(OutputInterface $output)
     private function migrateThreads(OutputInterface $output)
     {
         $cursor = $this->threadCollection->find(
-            array('metadata' => array('$exists' => false)),
-            array(
+            ['metadata' => ['$exists' => false]],
+            [
                 'datesOfLastMessageWrittenByOtherParticipant' => 1,
                 'datesOfLastMessageWrittenByParticipant' => 1,
                 'isDeletedByParticipant' => 1,
                 'isSpam' => 1,
                 'messages' => 1,
-                'participants' => 1,
-            )
+                'participants' => 1
+            ]
         );
 
         $numProcessed = 0;
@@ -211,14 +208,14 @@ private function migrateThreads(OutputInterface $output)
                 $this->createThreadActiveParticipantArrays($thread);
 
                 $this->threadCollection->update(
-                    array('_id' => $thread['_id']),
-                    array('$set' => array(
+                    ['_id' => $thread['_id']],
+                    ['$set' => [
                         'activeParticipants' => $thread['activeParticipants'],
                         'activeRecipients' => $thread['activeRecipients'],
                         'activeSenders' => $thread['activeSenders'],
                         'lastMessageDate' => $thread['lastMessageDate'],
-                        'metadata' => $thread['metadata'],
-                    )),
+                        'metadata' => $thread['metadata']
+                    ]],
                     $this->updateOptions
                 );
                 ++$numProcessed;
@@ -237,13 +234,13 @@ private function migrateThreads(OutputInterface $output)
      */
     private function createMessageMetadata(array &$message)
     {
-        $metadata = array();
+        $metadata = [];
 
         foreach ($message['isReadByParticipant'] as $participantId => $isRead) {
-            $metadata[] = array(
+            $metadata[] = [
                 'isRead' => $isRead,
-                'participant' => $this->participantCollection->createDBRef(array('_id' => new \MongoId($participantId))) + array('$db' => (string) $this->participantCollection->db),
-            );
+                'participant' => $this->participantCollection->createDBRef(['_id' => new \MongoId($participantId)]) + ['$db' => (string) $this->participantCollection->db]
+            ];
         }
 
         $message['metadata'] = $metadata;
@@ -258,7 +255,7 @@ private function createMessageMetadata(array &$message)
      */
     private function createMessageUnreadForParticipants(array &$message)
     {
-        $unreadForParticipants = array();
+        $unreadForParticipants = [];
 
         if (!$message['isSpam']) {
             foreach ($message['metadata'] as $metadata) {
@@ -281,15 +278,12 @@ private function createMessageUnreadForParticipants(array &$message)
      */
     private function createThreadMetadata(array &$thread)
     {
-        $metadata = array();
+        $metadata = [];
 
         $participantIds = array_keys($thread['datesOfLastMessageWrittenByOtherParticipant'] + $thread['datesOfLastMessageWrittenByParticipant'] + $thread['isDeletedByParticipant']);
 
         foreach ($participantIds as $participantId) {
-            $meta = array(
-                'isDeleted' => false,
-                'participant' => $this->participantCollection->createDBRef(array('_id' => new \MongoId($participantId))) + array('$db' => (string) $this->participantCollection->db),
-            );
+            $meta = ['isDeleted' => false, 'participant' => $this->participantCollection->createDBRef(['_id' => new \MongoId($participantId)]) + ['$db' => (string) $this->participantCollection->db]];
 
             if (isset($thread['isDeletedByParticipant'][$participantId])) {
                 $meta['isDeleted'] = $thread['isDeletedByParticipant'][$participantId];
@@ -320,8 +314,8 @@ private function createThreadLastMessageDate(array &$thread)
 
         if (false !== $lastMessageRef) {
             $lastMessage = $this->messageCollection->findOne(
-                array('_id' => $lastMessageRef['$id']),
-                array('createdAt' => 1)
+                ['_id' => $lastMessageRef['$id']],
+                ['createdAt' => 1]
             );
         }
 
@@ -337,9 +331,9 @@ private function createThreadLastMessageDate(array &$thread)
      */
     private function createThreadActiveParticipantArrays(array &$thread)
     {
-        $activeParticipants = array();
-        $activeRecipients = array();
-        $activeSenders = array();
+        $activeParticipants = [];
+        $activeRecipients = [];
+        $activeSenders = [];
 
         foreach ($thread['participants'] as $participantRef) {
             foreach ($thread['metadata'] as $metadata) {
diff --git a/Controller/MessageController.php b/Controller/MessageController.php
index 9fdcfbbc..ac582334 100644
--- a/Controller/MessageController.php
+++ b/Controller/MessageController.php
@@ -2,23 +2,85 @@
 
 namespace FOS\MessageBundle\Controller;
 
+use FOS\MessageBundle\Deleter\DeleterInterface;
+use FOS\MessageBundle\FormFactory\FactoryInterface;
+use FOS\MessageBundle\FormHandler\FormHandlerInterface;
+use FOS\MessageBundle\ModelManager\ThreadManagerInterface;
 use FOS\MessageBundle\Provider\ProviderInterface;
+use FOS\MessageBundle\Search\FinderInterface;
+use FOS\MessageBundle\Search\QueryFactoryInterface;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
 use Symfony\Component\HttpFoundation\RedirectResponse;
 use Symfony\Component\HttpFoundation\Response;
-use Symfony\Component\DependencyInjection\ContainerInterface;
 
 class MessageController extends AbstractController
 {
-    public function __construct(ContainerInterface $container)
-    {
-        $this->setContainer($container);
-    }
+    /**
+     * @var ProviderInterface
+     */
+    protected $provider;
 
     /**
-     * @var ContainerInterface
+     * @var FactoryInterface
      */
-    protected $container;
+    protected $replyFormfactory;
+
+    /**
+     * @var FormHandlerInterface
+     */
+    protected $replyFormHandler;
+
+    /**
+     * @var FactoryInterface
+     */
+    protected $newThreadFormFactory;
+
+    /**
+     * @var FormHandlerInterface
+     */
+    protected $newThreadFormHandler;
+
+    /**
+     * @var DeleterInterface
+     */
+    protected $deleter;
+
+    /**
+     * @var ThreadManagerInterface
+     */
+    protected $threadManager;
+
+    /**
+     * @var QueryFactoryInterface
+     */
+    protected $queryFactory;
+
+    /**
+     * @var FinderInterface
+     */
+    protected $finder;
+
+    public function __construct(
+        ProviderInterface $provider,
+        FactoryInterface $replyFormfactory,
+        FormHandlerInterface $replyFormHandler,
+        FactoryInterface $newThreadFormFactory,
+        FormHandlerInterface $newThreadFormHandler,
+        DeleterInterface $deleter,
+        ThreadManagerInterface $threadManager,
+        QueryFactoryInterface $queryFactory,
+        FinderInterface $finder
+    ) {
+        $this->provider = $provider;
+        $this->replyFormfactory = $replyFormfactory;
+        $this->replyFormHandler = $replyFormHandler;
+        $this->newThreadFormFactory = $newThreadFormFactory;
+        $this->newThreadFormHandler = $newThreadFormHandler;
+        $this->deleter = $deleter;
+        $this->threadManager = $threadManager;
+        $this->queryFactory = $queryFactory;
+        $this->finder = $finder;
+    }
 
     /**
      * Displays the authenticated participant inbox.
@@ -27,11 +89,9 @@ public function __construct(ContainerInterface $container)
      */
     public function inboxAction()
     {
-        $threads = $this->getProvider()->getInboxThreads();
+        $threads = $this->provider->getInboxThreads();
 
-        return $this->render('@FOSMessage/Message/inbox.html.twig', array(
-            'threads' => $threads,
-        ));
+        return $this->render('@FOSMessage/Message/inbox.html.twig', ['threads' => $threads]);
     }
 
     /**
@@ -41,11 +101,9 @@ public function inboxAction()
      */
     public function sentAction()
     {
-        $threads = $this->getProvider()->getSentThreads();
+        $threads = $this->provider->getSentThreads();
 
-        return $this->render('@FOSMessage/Message/sent.html.twig', array(
-            'threads' => $threads,
-        ));
+        return $this->render('@FOSMessage/Message/sent.html.twig', ['threads' => $threads]);
     }
 
     /**
@@ -55,11 +113,9 @@ public function sentAction()
      */
     public function deletedAction()
     {
-        $threads = $this->getProvider()->getDeletedThreads();
+        $threads = $this->provider->getDeletedThreads();
 
-        return $this->render('@FOSMessage/Message/deleted.html.twig', array(
-            'threads' => $threads,
-        ));
+        return $this->render('@FOSMessage/Message/deleted.html.twig', ['threads' => $threads]);
     }
 
     /**
@@ -71,20 +127,17 @@ public function deletedAction()
      */
     public function threadAction($threadId)
     {
-        $thread = $this->getProvider()->getThread($threadId);
-        $form = $this->container->get('fos_message.reply_form.factory')->create($thread);
-        $formHandler = $this->container->get('fos_message.reply_form.handler');
-
-        if ($message = $formHandler->process($form)) {
-            return new RedirectResponse($this->container->get('router')->generate('fos_message_thread_view', array(
-                'threadId' => $message->getThread()->getId(),
-            )));
+        $thread = $this->provider->getThread($threadId);
+        $form = $this->replyFormfactory->create($thread);
+
+        if ($message = $this->replyFormHandler->process($form)) {
+            return $this->redirectToRoute('fos_message_thread_view', ['threadId' => $message->getThread()->getId()]);
         }
 
-        return $this->render('@FOSMessage/Message/thread.html.twig', array(
+        return $this->render('@FOSMessage/Message/thread.html.twig', [
             'form' => $form->createView(),
-            'thread' => $thread,
-        ));
+            'thread' => $thread
+        ]);
     }
 
     /**
@@ -94,19 +147,16 @@ public function threadAction($threadId)
      */
     public function newThreadAction()
     {
-        $form = $this->container->get('fos_message.new_thread_form.factory')->create();
-        $formHandler = $this->container->get('fos_message.new_thread_form.handler');
+        $form = $this->newThreadFormFactory->create();
 
-        if ($message = $formHandler->process($form)) {
-            return new RedirectResponse($this->container->get('router')->generate('fos_message_thread_view', array(
-                'threadId' => $message->getThread()->getId(),
-            )));
+        if ($message = $this->newThreadFormHandler->process($form)) {
+            return $this->redirectToRoute('fos_message_thread_view', ['threadId' => $message->getThread()->getId()]);
         }
 
-        return $this->render('@FOSMessage/Message/newThread.html.twig', array(
+        return $this->render('@FOSMessage/Message/newThread.html.twig', [
             'form' => $form->createView(),
-            'data' => $form->getData(),
-        ));
+            'data' => $form->getData()
+        ]);
     }
 
     /**
@@ -118,11 +168,11 @@ public function newThreadAction()
      */
     public function deleteAction($threadId)
     {
-        $thread = $this->getProvider()->getThread($threadId);
-        $this->container->get('fos_message.deleter')->markAsDeleted($thread);
-        $this->container->get('fos_message.thread_manager')->saveThread($thread);
+        $thread = $this->provider->getThread($threadId);
+        $this->deleter->markAsDeleted($thread);
+        $this->threadManager->saveThread($thread);
 
-        return new RedirectResponse($this->container->get('router')->generate('fos_message_inbox'));
+        return $this->redirectToRoute('fos_message_inbox');
     }
 
     /**
@@ -132,13 +182,13 @@ public function deleteAction($threadId)
      *
      * @return RedirectResponse
      */
-    public function undeleteAction($threadId)
+    public function undeleteAction($threadId, DeleterInterface $deleter, ThreadManagerInterface $threadManager)
     {
-        $thread = $this->getProvider()->getThread($threadId);
-        $this->container->get('fos_message.deleter')->markAsUndeleted($thread);
-        $this->container->get('fos_message.thread_manager')->saveThread($thread);
+        $thread = $this->provider->getThread($threadId);
+        $deleter->markAsUndeleted($thread);
+        $threadManager->saveThread($thread);
 
-        return new RedirectResponse($this->container->get('router')->generate('fos_message_inbox'));
+        return $this->redirectToRoute('fos_message_inbox');
     }
 
     /**
@@ -148,22 +198,9 @@ public function undeleteAction($threadId)
      */
     public function searchAction()
     {
-        $query = $this->container->get('fos_message.search_query_factory')->createFromRequest();
-        $threads = $this->container->get('fos_message.search_finder')->find($query);
-
-        return $this->render('@FOSMessage/Message/search.html.twig', array(
-            'query' => $query,
-            'threads' => $threads,
-        ));
-    }
+        $query = $this->queryFactory->createFromRequest();
+        $threads = $this->finder->find($query);
 
-    /**
-     * Gets the provider service.
-     *
-     * @return ProviderInterface
-     */
-    protected function getProvider()
-    {
-        return $this->container->get('fos_message.provider');
+        return $this->render('@FOSMessage/Message/search.html.twig', ['query' => $query, 'threads' => $threads]);
     }
 }
diff --git a/DataTransformer/RecipientsDataTransformer.php b/DataTransformer/RecipientsDataTransformer.php
index 02c7809d..a0242c56 100644
--- a/DataTransformer/RecipientsDataTransformer.php
+++ b/DataTransformer/RecipientsDataTransformer.php
@@ -33,13 +33,13 @@ public function __construct(DataTransformerInterface $userToUsernameTransformer)
      *
      * @return string
      */
-    public function transform($recipients)
+    public function transform($recipients): mixed
     {
         if (null === $recipients || 0 === $recipients->count()) {
             return '';
         }
 
-        $usernames = array();
+        $usernames = [];
 
         foreach ($recipients as $recipient) {
             $usernames[] = $this->userToUsernameTransformer->transform($recipient);
diff --git a/Deleter/Deleter.php b/Deleter/Deleter.php
index b9685337..d0e8fade 100644
--- a/Deleter/Deleter.php
+++ b/Deleter/Deleter.php
@@ -56,7 +56,7 @@ public function markAsDeleted(ThreadInterface $thread)
         }
         $thread->setIsDeletedByParticipant($this->getAuthenticatedParticipant(), true);
 
-        $this->dispatcher->dispatch(FOSMessageEvents::POST_DELETE, new ThreadEvent($thread));
+        $this->dispatcher->dispatch(new ThreadEvent($thread), FOSMessageEvents::POST_DELETE);
     }
 
     /**
@@ -69,7 +69,7 @@ public function markAsUndeleted(ThreadInterface $thread)
         }
         $thread->setIsDeletedByParticipant($this->getAuthenticatedParticipant(), false);
 
-        $this->dispatcher->dispatch(FOSMessageEvents::POST_UNDELETE, new ThreadEvent($thread));
+        $this->dispatcher->dispatch(new ThreadEvent($thread), FOSMessageEvents::POST_UNDELETE);
     }
 
     /**
diff --git a/DependencyInjection/Configuration.php b/DependencyInjection/Configuration.php
index bc39b192..bae5c758 100644
--- a/DependencyInjection/Configuration.php
+++ b/DependencyInjection/Configuration.php
@@ -26,7 +26,7 @@ public function getConfigTreeBuilder()
             $rootNode = $treeBuilder->root(self::ROOT_NAME);
         }
 
-        $rootNode
+        $treeBuilder->getRootNode()
             ->children()
                 ->scalarNode('db_driver')->cannotBeOverwritten()->isRequired()->cannotBeEmpty()->end()
                 ->scalarNode('thread_class')->isRequired()->cannotBeEmpty()->end()
@@ -47,8 +47,8 @@ public function getConfigTreeBuilder()
                 ->arrayNode('search')
                     ->addDefaultsIfNotSet()
                     ->children()
-                        ->scalarNode('query_factory')->defaultValue('fos_message.search_query_factory.default')->cannotBeEmpty()->end()
-                        ->scalarNode('finder')->defaultValue('fos_message.search_finder.default')->cannotBeEmpty()->end()
+                        ->scalarNode('query_factory')->defaultValue('fos_message.search.query_factory.default')->cannotBeEmpty()->end()
+                        ->scalarNode('finder')->defaultValue('fos_message.search.finder.default')->cannotBeEmpty()->end()
                         ->scalarNode('query_parameter')->defaultValue('q')->cannotBeEmpty()->end()
                     ->end()
                 ->end()
diff --git a/DependencyInjection/FOSMessageExtension.php b/DependencyInjection/FOSMessageExtension.php
index 169f3b82..e895a85b 100644
--- a/DependencyInjection/FOSMessageExtension.php
+++ b/DependencyInjection/FOSMessageExtension.php
@@ -21,7 +21,7 @@ public function load(array $configs, ContainerBuilder $container)
 
         $loader = new XmlFileLoader($container, new FileLocator(__DIR__.'/../Resources/config'));
 
-        if (!in_array(strtolower($config['db_driver']), array('orm', 'mongodb'))) {
+        if (!in_array(strtolower($config['db_driver']), ['orm', 'mongodb'])) {
             throw new \InvalidArgumentException(sprintf('Invalid db driver "%s".', $config['db_driver']));
         }
 
@@ -84,9 +84,9 @@ public function load(array $configs, ContainerBuilder $container)
         $container->setAlias('fos_message.reply_form.factory', new Alias($config['reply_form']['factory'], true));
         $container->setAlias('fos_message.reply_form.handler', new Alias($config['reply_form']['handler'], true));
 
-        $container->setAlias('fos_message.search_query_factory', new Alias($config['search']['query_factory'], true));
-        $container->setAlias('fos_message.search_finder', new Alias($config['search']['finder'], true));
-        $container->getDefinition('fos_message.search_query_factory.default')
+        $container->setAlias('fos_message.search.query_factory', new Alias($config['search']['query_factory'], true));
+        $container->setAlias('fos_message.search.finder', new Alias($config['search']['finder'], true));
+        $container->getDefinition('fos_message.search.query_factory.default')
             ->replaceArgument(1, $config['search']['query_parameter']);
 
         $container->getDefinition('fos_message.recipients_data_transformer')
diff --git a/Document/Message.php b/Document/Message.php
index c92760ff..443d2d44 100644
--- a/Document/Message.php
+++ b/Document/Message.php
@@ -20,7 +20,7 @@ abstract class Message extends BaseMessage
      *
      * @var array of participant ID's
      */
-    protected $unreadForParticipants = array();
+    protected $unreadForParticipants = [];
 
     /**
      * @param bool $isSpam
@@ -58,7 +58,7 @@ protected function doSenderIsRead()
      */
     protected function doEnsureUnreadForParticipantsArray()
     {
-        $this->unreadForParticipants = array();
+        $this->unreadForParticipants = [];
 
         if ($this->isSpam) {
             return;
diff --git a/Document/Thread.php b/Document/Thread.php
index 237a072d..a70d5c4c 100644
--- a/Document/Thread.php
+++ b/Document/Thread.php
@@ -31,7 +31,7 @@ abstract class Thread extends AbstractThread
      *
      * @var array of participant ID's
      */
-    protected $activeParticipants = array();
+    protected $activeParticipants = [];
 
     /**
      * The activeRecipients array will contain a participant's ID if the thread
@@ -40,7 +40,7 @@ abstract class Thread extends AbstractThread
      *
      * @var array of participant ID's
      */
-    protected $activeRecipients = array();
+    protected $activeRecipients = [];
 
     /**
      * The activeSenders array will contain a participant's ID if the thread is
@@ -49,7 +49,7 @@ abstract class Thread extends AbstractThread
      *
      * @var array of participant ID's
      */
-    protected $activeSenders = array();
+    protected $activeSenders = [];
 
     /**
      * Gets the users participating in this conversation.
@@ -186,9 +186,9 @@ protected function doMetadataLastMessageDates()
      */
     protected function doEnsureActiveParticipantArrays()
     {
-        $this->activeParticipants = array();
-        $this->activeRecipients = array();
-        $this->activeSenders = array();
+        $this->activeParticipants = [];
+        $this->activeRecipients = [];
+        $this->activeSenders = [];
 
         foreach ($this->getParticipants() as $participant) {
             if ($this->isDeletedByParticipant($participant)) {
diff --git a/DocumentManager/MessageManager.php b/DocumentManager/MessageManager.php
index 0b2c9c59..21bac32c 100644
--- a/DocumentManager/MessageManager.php
+++ b/DocumentManager/MessageManager.php
@@ -133,7 +133,7 @@ protected function markIsReadByCondition(ParticipantInterface $participant, $isR
 
         $queryBuilder
             ->field('metadata.$.isRead')->set((bool) $isRead)
-            ->getQuery(array('multiple' => true))
+            ->getQuery(['multiple' => true])
             ->execute();
 
         /* If marking the message as unread for a participant, add their ID to
@@ -147,7 +147,7 @@ protected function markIsReadByCondition(ParticipantInterface $participant, $isR
                 ->field('metadata.participant.$id')->equals(new \MongoId($participant->getId()))
                 ->field('isSpam')->equals(false)
                 ->field('unreadForParticipants')->addToSet($participant->getId())
-                ->getQuery(array('multiple' => true))
+                ->getQuery(['multiple' => true])
                 ->execute();
         }
     }
diff --git a/Event/ReadableEvent.php b/Event/ReadableEvent.php
index 3f9e18c6..3cc17083 100644
--- a/Event/ReadableEvent.php
+++ b/Event/ReadableEvent.php
@@ -3,7 +3,7 @@
 namespace FOS\MessageBundle\Event;
 
 use FOS\MessageBundle\Model\ReadableInterface;
-use Symfony\Component\EventDispatcher\Event;
+use Symfony\Contracts\EventDispatcher\Event;
 
 class ReadableEvent extends Event
 {
diff --git a/Event/ThreadEvent.php b/Event/ThreadEvent.php
index b7176180..0ae3fa7c 100644
--- a/Event/ThreadEvent.php
+++ b/Event/ThreadEvent.php
@@ -3,7 +3,7 @@
 namespace FOS\MessageBundle\Event;
 
 use FOS\MessageBundle\Model\ThreadInterface;
-use Symfony\Component\EventDispatcher\Event;
+use Symfony\Contracts\EventDispatcher\Event;
 
 class ThreadEvent extends Event
 {
diff --git a/FormFactory/AbstractMessageFormFactory.php b/FormFactory/AbstractMessageFormFactory.php
index fe6ace22..e0ae3801 100644
--- a/FormFactory/AbstractMessageFormFactory.php
+++ b/FormFactory/AbstractMessageFormFactory.php
@@ -11,7 +11,7 @@
  *
  * @author Thibault Duplessis <thibault.duplessis@gmail.com>
  */
-abstract class AbstractMessageFormFactory
+abstract class AbstractMessageFormFactory implements FactoryInterface
 {
     /**
      * The Symfony form factory.
diff --git a/FormFactory/FactoryInterface.php b/FormFactory/FactoryInterface.php
new file mode 100644
index 00000000..309d0af1
--- /dev/null
+++ b/FormFactory/FactoryInterface.php
@@ -0,0 +1,14 @@
+<?php
+
+namespace FOS\MessageBundle\FormFactory;
+
+use FOS\MessageBundle\Model\ThreadInterface;
+use Symfony\Component\Form\FormInterface;
+
+interface FactoryInterface
+{
+    /**
+     * @return FormInterface
+     */
+    public function create(?ThreadInterface $thread = null);
+}
diff --git a/FormFactory/NewThreadMessageFormFactory.php b/FormFactory/NewThreadMessageFormFactory.php
index 271beda5..f7640979 100644
--- a/FormFactory/NewThreadMessageFormFactory.php
+++ b/FormFactory/NewThreadMessageFormFactory.php
@@ -2,6 +2,7 @@
 
 namespace FOS\MessageBundle\FormFactory;
 
+use FOS\MessageBundle\Model\ThreadInterface;
 use Symfony\Component\Form\FormInterface;
 
 /**
@@ -16,7 +17,7 @@ class NewThreadMessageFormFactory extends AbstractMessageFormFactory
      *
      * @return FormInterface
      */
-    public function create()
+    public function create(?ThreadInterface $thread = null)
     {
         return $this->formFactory->createNamed($this->formName, $this->formType, $this->createModelInstance());
     }
diff --git a/FormFactory/ReplyMessageFormFactory.php b/FormFactory/ReplyMessageFormFactory.php
index 27cc599a..89632899 100644
--- a/FormFactory/ReplyMessageFormFactory.php
+++ b/FormFactory/ReplyMessageFormFactory.php
@@ -19,7 +19,7 @@ class ReplyMessageFormFactory extends AbstractMessageFormFactory
      *
      * @return FormInterface
      */
-    public function create(ThreadInterface $thread)
+    public function create(?ThreadInterface $thread = null)
     {
         $message = $this->createModelInstance();
         $message->setThread($thread);
diff --git a/FormHandler/AbstractMessageFormHandler.php b/FormHandler/AbstractMessageFormHandler.php
index 08e3aa75..32a9c79c 100644
--- a/FormHandler/AbstractMessageFormHandler.php
+++ b/FormHandler/AbstractMessageFormHandler.php
@@ -17,7 +17,7 @@
  *
  * @author Thibault Duplessis <thibault.duplessis@gmail.com>
  */
-abstract class AbstractMessageFormHandler
+abstract class AbstractMessageFormHandler implements FormHandlerInterface
 {
     protected $request;
     protected $composer;
diff --git a/FormHandler/FormHandlerInterface.php b/FormHandler/FormHandlerInterface.php
new file mode 100644
index 00000000..b6545516
--- /dev/null
+++ b/FormHandler/FormHandlerInterface.php
@@ -0,0 +1,27 @@
+<?php
+
+namespace FOS\MessageBundle\FormHandler;
+
+use FOS\MessageBundle\Model\MessageInterface;
+use Symfony\Component\Form\Form;
+
+interface FormHandlerInterface
+{
+    /**
+     * Processes the form with the request.
+     *
+     * @param Form $form
+     *
+     * @return MessageInterface|false the sent message if the form is bound and valid, false otherwise
+     */
+    public function process(Form $form);
+
+    /**
+     * Processes the valid form, sends the message.
+     *
+     * @param Form $form
+     *
+     * @return MessageInterface the sent message
+     */
+    public function processValidForm(Form $form);
+}
\ No newline at end of file
diff --git a/FormType/NewThreadMessageFormType.php b/FormType/NewThreadMessageFormType.php
index 7acfc1fe..45d45535 100644
--- a/FormType/NewThreadMessageFormType.php
+++ b/FormType/NewThreadMessageFormType.php
@@ -18,31 +18,29 @@ class NewThreadMessageFormType extends AbstractType
     public function buildForm(FormBuilderInterface $builder, array $options)
     {
         $builder
-            ->add('recipient', LegacyFormHelper::getType('FOS\UserBundle\Form\Type\UsernameFormType'), array(
+            ->add('recipient', LegacyFormHelper::getType('FOS\UserBundle\Form\Type\UsernameFormType'), [
                 'label' => 'recipient',
-                'translation_domain' => 'FOSMessageBundle',
-            ))
-            ->add('subject', LegacyFormHelper::getType('Symfony\Component\Form\Extension\Core\Type\TextType'), array(
+                'translation_domain' => 'FOSMessageBundle'
+            ])
+            ->add('subject', LegacyFormHelper::getType('Symfony\Component\Form\Extension\Core\Type\TextType'), [
                 'label' => 'subject',
-                'translation_domain' => 'FOSMessageBundle',
-            ))
-            ->add('body', LegacyFormHelper::getType('Symfony\Component\Form\Extension\Core\Type\TextareaType'), array(
+                'translation_domain' => 'FOSMessageBundle'
+            ])
+            ->add('body', LegacyFormHelper::getType('Symfony\Component\Form\Extension\Core\Type\TextareaType'), [
                 'label' => 'body',
-                'translation_domain' => 'FOSMessageBundle',
-            ));
+                'translation_domain' => 'FOSMessageBundle'
+            ]);
     }
 
     public function configureOptions(OptionsResolver $resolver)
     {
-        $resolver->setDefaults(array(
-            'intention' => 'message',
-        ));
+        $resolver->setDefaults(['intention' => 'message']);
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getBlockPrefix()
+    public function getBlockPrefix(): string
     {
         return 'fos_message_new_thread';
     }
diff --git a/FormType/NewThreadMultipleMessageFormType.php b/FormType/NewThreadMultipleMessageFormType.php
index 51a1bcbe..19582fe8 100644
--- a/FormType/NewThreadMultipleMessageFormType.php
+++ b/FormType/NewThreadMultipleMessageFormType.php
@@ -16,24 +16,24 @@ class NewThreadMultipleMessageFormType extends AbstractType
     public function buildForm(FormBuilderInterface $builder, array $options)
     {
         $builder
-            ->add('recipients', LegacyFormHelper::getType('FOS\MessageBundle\FormType\RecipientsType'), array(
+            ->add('recipients', LegacyFormHelper::getType('FOS\MessageBundle\FormType\RecipientsType'), [
                 'label' => 'recipients',
-                'translation_domain' => 'FOSMessageBundle',
-            ))
-            ->add('subject', LegacyFormHelper::getType('Symfony\Component\Form\Extension\Core\Type\TextType'), array(
+                'translation_domain' => 'FOSMessageBundle'
+            ])
+            ->add('subject', LegacyFormHelper::getType('Symfony\Component\Form\Extension\Core\Type\TextType'), [
                 'label' => 'subject',
-                'translation_domain' => 'FOSMessageBundle',
-            ))
-            ->add('body', LegacyFormHelper::getType('Symfony\Component\Form\Extension\Core\Type\TextareaType'), array(
+                'translation_domain' => 'FOSMessageBundle'
+            ])
+            ->add('body', LegacyFormHelper::getType('Symfony\Component\Form\Extension\Core\Type\TextareaType'), [
                 'label' => 'body',
-                'translation_domain' => 'FOSMessageBundle',
-            ));
+                'translation_domain' => 'FOSMessageBundle'
+            ]);
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getBlockPrefix()
+    public function getBlockPrefix(): string
     {
         return 'fos_message_new_multiperson_thread';
     }
diff --git a/FormType/RecipientsType.php b/FormType/RecipientsType.php
index 6a1fe369..43cd8ad6 100644
--- a/FormType/RecipientsType.php
+++ b/FormType/RecipientsType.php
@@ -42,9 +42,7 @@ public function buildForm(FormBuilderInterface $builder, array $options)
      */
     public function configureOptions(OptionsResolver $resolver)
     {
-        $resolver->setDefaults(array(
-            'invalid_message' => 'The selected recipient does not exist',
-        ));
+        $resolver->setDefaults(['invalid_message' => 'The selected recipient does not exist']);
     }
 
     public function setDefaultOptions(OptionsResolverInterface $resolver)
@@ -55,7 +53,7 @@ public function setDefaultOptions(OptionsResolverInterface $resolver)
     /**
      * {@inheritdoc}
      */
-    public function getBlockPrefix()
+    public function getBlockPrefix(): string
     {
         return 'recipients_selector';
     }
@@ -63,7 +61,7 @@ public function getBlockPrefix()
     /**
      * {@inheritdoc}
      */
-    public function getParent()
+    public function getParent(): ?string
     {
         return LegacyFormHelper::getType('Symfony\Component\Form\Extension\Core\Type\TextType');
     }
diff --git a/FormType/ReplyMessageFormType.php b/FormType/ReplyMessageFormType.php
index 3d1592e5..83a42709 100644
--- a/FormType/ReplyMessageFormType.php
+++ b/FormType/ReplyMessageFormType.php
@@ -18,23 +18,22 @@ class ReplyMessageFormType extends AbstractType
     public function buildForm(FormBuilderInterface $builder, array $options)
     {
         $builder
-            ->add('body', LegacyFormHelper::getType('Symfony\Component\Form\Extension\Core\Type\TextareaType'), array(
+            ->add('body', LegacyFormHelper::getType('Symfony\Component\Form\Extension\Core\Type\TextareaType'), [
                 'label' => 'body',
-                'translation_domain' => 'FOSMessageBundle',
-            ));
+                'translation_domain' => 'FOSMessageBundle'
+            ]
+        );
     }
 
     public function configureOptions(OptionsResolver $resolver)
     {
-        $resolver->setDefaults(array(
-            'intention' => 'reply',
-        ));
+        $resolver->setDefaults(['intention' => 'reply']);
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getBlockPrefix()
+    public function getBlockPrefix(): string
     {
         return 'fos_message_reply_message';
     }
diff --git a/Model/ParticipantInterface.php b/Model/ParticipantInterface.php
index 6849dec9..b8d10011 100644
--- a/Model/ParticipantInterface.php
+++ b/Model/ParticipantInterface.php
@@ -9,7 +9,7 @@
  *
  * @author Thibault Duplessis <thibault.duplessis@gmail.com>
  */
-interface ParticipantInterface
+interface ParticipantInterface extends \Stringable
 {
     /**
      * Gets the unique identifier of the participant.
diff --git a/Reader/Reader.php b/Reader/Reader.php
index f0a25812..a45052a8 100644
--- a/Reader/Reader.php
+++ b/Reader/Reader.php
@@ -56,7 +56,7 @@ public function markAsRead(ReadableInterface $readable)
         }
         $this->readableManager->markAsReadByParticipant($readable, $participant);
 
-        $this->dispatcher->dispatch(FOSMessageEvents::POST_READ, new ReadableEvent($readable));
+        $this->dispatcher->dispatch(new ReadableEvent($readable), FOSMessageEvents::POST_READ);
     }
 
     /**
@@ -70,7 +70,7 @@ public function markAsUnread(ReadableInterface $readable)
         }
         $this->readableManager->markAsUnreadByParticipant($readable, $participant);
 
-        $this->dispatcher->dispatch(FOSMessageEvents::POST_UNREAD, new ReadableEvent($readable));
+        $this->dispatcher->dispatch(new ReadableEvent($readable), FOSMessageEvents::POST_UNREAD);
     }
 
     /**
diff --git a/Resources/config/config.xml b/Resources/config/config.xml
index 7acf5474..fbcb30a6 100644
--- a/Resources/config/config.xml
+++ b/Resources/config/config.xml
@@ -5,12 +5,20 @@
     xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">
 
     <services>
-
         <service id="FOS\MessageBundle\Controller\MessageController" public="true">
-            <bind key="$container"
-                type="service"
-                id="service_container"
-            />
+            <bind key="$provider" type="service" id="fos_message.provider" />
+            <bind key="$replyFormfactory" type="service" id="fos_message.reply_form.factory" />
+            <bind key="$replyFormHandler" type="service" id="fos_message.reply_form.handler" />
+            <bind key="$newThreadFormFactory" type="service" id="fos_message.new_thread_form.factory" />
+            <bind key="$newThreadFormHandler" type="service" id="fos_message.new_thread_form.handler" />
+            <bind key="$deleter" type="service" id="fos_message.deleter" />
+            <bind key="$threadManager" type="service" id="fos_message.thread_manager" />
+            <bind key="$queryFactory" type="service" id="fos_message.search.query_factory" />
+            <bind key="$finder" type="service" id="fos_message.search.finder" />
+            <call method="setContainer">
+                <argument type="service" id="Psr\Container\ContainerInterface" />
+            </call>
+            <tag name="container.service_subscriber" />
         </service>
 
         <service id="fos_message.sender.default" class="FOS\MessageBundle\Sender\Sender" public="false">
@@ -58,19 +66,19 @@
             <argument type="service" id="event_dispatcher" />
         </service>
 
-        <service id="fos_message.twig_extension.default" class="FOS\MessageBundle\Twig\Extension\MessageExtension" public="false">
+        <service id="fos_message.twig_extension.default" class="FOS\MessageBundle\Twig\MessageExtension" public="false">
             <argument type="service" id="fos_message.participant_provider" />
             <argument type="service" id="fos_message.provider" />
             <argument type="service" id="fos_message.authorizer" />
             <tag name="twig.extension" alias="fos_message" />
         </service>
 
-        <service id="fos_message.search_query_factory.default" class="FOS\MessageBundle\Search\QueryFactory" public="true">
+        <service id="fos_message.search.query_factory.default" class="FOS\MessageBundle\Search\QueryFactory" public="true">
             <argument type="service" id="request_stack" />
             <argument /> <!-- query parameter containing the search terms -->
         </service>
 
-        <service id="fos_message.search_finder.default" class="FOS\MessageBundle\Search\Finder" public="true">
+        <service id="fos_message.search.finder.default" class="FOS\MessageBundle\Search\Finder" public="true">
             <argument type="service" id="fos_message.participant_provider" />
             <argument type="service" id="fos_message.thread_manager" />
         </service>
diff --git a/Resources/doc/01-installation.md b/Resources/doc/01-installation.md
index 28ff3b11..e8a5b010 100644
--- a/Resources/doc/01-installation.md
+++ b/Resources/doc/01-installation.md
@@ -32,7 +32,7 @@ Your user class may look something like the following:
 
 ```php
 <?php
-// src/AppBundle/Entity/User.php
+// src/Entity/User.php
 
 use Doctrine\ORM\Mapping as ORM;
 use FOS\MessageBundle\Model\ParticipantInterface;
@@ -58,21 +58,18 @@ We provide examples for both Mongo DB and ORM.
 
 ### Step 4 - Enable the bundle in your kernel
 
-The bundle must be added to your `AppKernel`.
+The bundle must be added to your `bundles.php`.
 
 **Step usually not necescary in Symfony 4**.
 
 ```php
-// app/AppKernel.php
+// config/bundles.php
 
-public function registerBundles()
-{
-    return array(
-        // ...
-        new FOS\MessageBundle\FOSMessageBundle(),
-        // ...
-    );
-}
+return [
+    // ...
+    FOS\MessageBundle\FOSMessageBundle::class => ['all' => true],
+    // ...
+];
 ```
 
 ### Step 5 - Import the bundle routing
@@ -80,7 +77,7 @@ public function registerBundles()
 Add FOSMessageBundle's routing to your application with an optional routing prefix.
 
 ```yaml
-# app/config/routing.yml
+# config/routing.yaml
 
 fos_message:
     resource: "@FOSMessageBundle/Resources/config/routing.xml"
@@ -89,13 +86,7 @@ fos_message:
 
 ### Step 6 - Check templating
 
-Make sure to add this to `framwork.yaml` (and check twig is installed) if you run into the non-existant service `templating` issue:
-
-```yaml
-templating:
-    engines:
-        twig
-```
+Make sure to have twig installed and ready to be used
 
 
 ## Installation Finished
diff --git a/Resources/doc/01a-orm-models.md b/Resources/doc/01a-orm-models.md
index 4b3e2246..ba7d6189 100644
--- a/Resources/doc/01a-orm-models.md
+++ b/Resources/doc/01a-orm-models.md
@@ -7,15 +7,15 @@ ORM.
 Given the examples below with their namespaces and class names, you need to configure
 FOSMessageBundle to tell them about these classes.
 
-Add the following to your `app/config/config.yml` file.
+Create and add the following config to your `config/fos_message.yaml` file.
 
 ```yaml
-# app/config/config.yml
+# config/fos_message.yaml
 
 fos_message:
     db_driver: orm
-    thread_class: AppBundle\Entity\Thread
-    message_class: AppBundle\Entity\Message
+    thread_class: App\Entity\Thread
+    message_class: App\Entity\Message
 ```
 
 [Continue with the installation][]
@@ -25,49 +25,38 @@ Message class
 
 ```php
 <?php
-// src/AppBundle/Entity/Message.php
+// src/Entity/Message.php
 
-namespace AppBundle\Entity;
+namespace App\Entity;
 
 use Doctrine\ORM\Mapping as ORM;
 use Doctrine\Common\Collections\Collection;
 use FOS\MessageBundle\Entity\Message as BaseMessage;
 
-/**
- * @ORM\Entity
- */
+#[ORM\Entity]
 class Message extends BaseMessage
 {
-    /**
-     * @ORM\Id
-     * @ORM\Column(type="integer")
-     * @ORM\GeneratedValue(strategy="AUTO")
-     */
+    #[ORM\Id]
+    #[ORM\Column(type: 'integer')]
+    #[ORM\GeneratedValue(strategy: 'AUTO')]
     protected $id;
 
     /**
-     * @ORM\ManyToOne(
-     *   targetEntity="AppBundle\Entity\Thread",
-     *   inversedBy="messages"
-     * )
      * @var \FOS\MessageBundle\Model\ThreadInterface
      */
+    #[ORM\ManyToOne(targetEntity: 'App\Entity\Thread', inversedBy: 'messages')]
     protected $thread;
 
     /**
-     * @ORM\ManyToOne(targetEntity="AppBundle\Entity\User")
      * @var \FOS\MessageBundle\Model\ParticipantInterface
      */
+    #[ORM\ManyToOne(targetEntity: 'App\Entity\User')]
     protected $sender;
 
     /**
-     * @ORM\OneToMany(
-     *   targetEntity="AppBundle\Entity\MessageMetadata",
-     *   mappedBy="message",
-     *   cascade={"all"}
-     * )
      * @var MessageMetadata[]|Collection
      */
+    #[ORM\OneToMany(targetEntity: 'App\Entity\MessageMetadata', mappedBy: 'message', cascade: ['all'])]
     protected $metadata;
 }
 ```
@@ -77,38 +66,31 @@ MessageMetadata class
 
 ```php
 <?php
-// src/AppBundle/Entity/MessageMetadata.php
+// src/Entity/MessageMetadata.php
 
-namespace AppBundle\Entity;
+namespace App\Entity;
 
 use Doctrine\ORM\Mapping as ORM;
 use FOS\MessageBundle\Entity\MessageMetadata as BaseMessageMetadata;
 
-/**
- * @ORM\Entity
- */
+#[ORM\Entity]
 class MessageMetadata extends BaseMessageMetadata
 {
-    /**
-     * @ORM\Id
-     * @ORM\Column(type="integer")
-     * @ORM\GeneratedValue(strategy="AUTO")
-     */
+    #[ORM\Id]
+    #[ORM\Column(type: 'integer')]
+    #[ORM\GeneratedValue(strategy: 'AUTO')]
     protected $id;
 
     /**
-     * @ORM\ManyToOne(
-     *   targetEntity="AppBundle\Entity\Message",
-     *   inversedBy="metadata"
-     * )
      * @var \FOS\MessageBundle\Model\MessageInterface
      */
+    #[ORM\ManyToOne(targetEntity: 'App\Entity\Message', inversedBy: 'metadata')]
     protected $message;
 
     /**
-     * @ORM\ManyToOne(targetEntity="AppBundle\Entity\User")
      * @var \FOS\MessageBundle\Model\ParticipantInterface
      */
+    #[ORM\ManyToOne(targetEntity: 'App\Entity\User')]
     protected $participant;
 }
 ```
@@ -118,49 +100,38 @@ Thread class
 
 ```php
 <?php
-// src/AppBundle/Entity/Thread.php
+// src/Entity/Thread.php
 
-namespace AppBundle\Entity;
+namespace App\Entity;
 
 use Doctrine\ORM\Mapping as ORM;
 use Doctrine\Common\Collections\Collection;
 use FOS\MessageBundle\Entity\Thread as BaseThread;
 
-/**
- * @ORM\Entity
- */
+#[ORM\Entity]
 class Thread extends BaseThread
 {
-    /**
-     * @ORM\Id
-     * @ORM\Column(type="integer")
-     * @ORM\GeneratedValue(strategy="AUTO")
-     */
+    #[ORM\Id]
+    #[ORM\Column(type: 'integer')]
+    #[ORM\GeneratedValue(strategy: 'AUTO')]
     protected $id;
 
     /**
-     * @ORM\ManyToOne(targetEntity="AppBundle\Entity\User")
      * @var \FOS\MessageBundle\Model\ParticipantInterface
      */
+    #[ORM\ManyToOne(targetEntity: 'App\Entity\User')]
     protected $createdBy;
 
     /**
-     * @ORM\OneToMany(
-     *   targetEntity="AppBundle\Entity\Message",
-     *   mappedBy="thread"
-     * )
      * @var Message[]|Collection
      */
+    #[ORM\OneToMany(targetEntity: 'App\Entity\Message', mappedBy: 'thread')]
     protected $messages;
 
     /**
-     * @ORM\OneToMany(
-     *   targetEntity="AppBundle\Entity\ThreadMetadata",
-     *   mappedBy="thread",
-     *   cascade={"all"}
-     * )
      * @var ThreadMetadata[]|Collection
      */
+    #[ORM\OneToMany(targetEntity: 'App\Entity\ThreadMetadata', mappedBy: 'thread', cascade: ['all'])]
     protected $metadata;
 }
 ```
@@ -170,38 +141,31 @@ ThreadMetadata class
 
 ```php
 <?php
-// src/AppBundle/Entity/ThreadMetadata.php
+// src/Entity/ThreadMetadata.php
 
-namespace AppBundle\Entity;
+namespace App\Entity;
 
 use Doctrine\ORM\Mapping as ORM;
 use FOS\MessageBundle\Entity\ThreadMetadata as BaseThreadMetadata;
 
-/**
- * @ORM\Entity
- */
+#[ORM\Entity]
 class ThreadMetadata extends BaseThreadMetadata
 {
-    /**
-     * @ORM\Id
-     * @ORM\Column(type="integer")
-     * @ORM\GeneratedValue(strategy="AUTO")
-     */
+    #[ORM\Id]
+    #[ORM\Column(type: 'integer')]
+    #[ORM\GeneratedValue(strategy: 'AUTO')]
     protected $id;
 
     /**
-     * @ORM\ManyToOne(
-     *   targetEntity="AppBundle\Entity\Thread",
-     *   inversedBy="metadata"
-     * )
      * @var \FOS\MessageBundle\Model\ThreadInterface
      */
+    #[ORM\ManyToOne(targetEntity: 'App\Entity\Thread', inversedBy: 'metadata')]
     protected $thread;
 
     /**
-     * @ORM\ManyToOne(targetEntity="AppBundle\Entity\User")
      * @var \FOS\MessageBundle\Model\ParticipantInterface
      */
+    #[ORM\ManyToOne(targetEntity: 'App\Entity\User')]
     protected $participant;
 }
 ```
diff --git a/Resources/doc/01b-odm-models.md b/Resources/doc/01b-odm-models.md
index 58d881e8..1d3b14d6 100644
--- a/Resources/doc/01b-odm-models.md
+++ b/Resources/doc/01b-odm-models.md
@@ -7,22 +7,22 @@ MongoDB ODM.
 Given the examples below with their namespaces and class names, you need to configure
 FOSMessageBundle to tell them about these classes.
 
-Add the following to your `app/config/config.yml` file.
+Add the following to your `config/fos_message.yaml` file.
 
 ```yaml
-# app/config/config.yml
+# config/fos_message.yaml
 
 fos_message:
     db_driver: mongodb
-    thread_class: AppBundle\Document\Thread
-    message_class: AppBundle\Document\Message
+    thread_class: App\Document\Thread
+    message_class: App\Document\Message
 ```
 
 You may have to include the MessageBundle in your Doctrine mapping configuration,
 along with the bundle containing your custom Thread and Message classes:
 
 ```yaml
-# app/config/config.yml
+# config/doctrine.yaml
 
 doctrine_mongodb:
     document_managers:
@@ -39,9 +39,9 @@ Message class
 
 ```php
 <?php
-// src/AppBundle/Document/Message.php
+// src/Document/Message.php
 
-namespace AppBundle\Document;
+namespace App\Document;
 
 use Doctrine\ODM\MongoDB\Mapping\Annotations as MongoDB;
 use FOS\MessageBundle\Document\Message as BaseMessage;
@@ -57,17 +57,17 @@ class Message extends BaseMessage
     protected $id;
 
     /**
-     * @MongoDB\EmbedMany(targetDocument="AppBundle\Document\MessageMetadata")
+     * @MongoDB\EmbedMany(targetDocument="App\Document\MessageMetadata")
      */
     protected $metadata;
 
     /**
-     * @MongoDB\ReferenceOne(targetDocument="AppBundle\Document\Thread")
+     * @MongoDB\ReferenceOne(targetDocument="App\Document\Thread")
      */
     protected $thread;
 
     /**
-     * @MongoDB\ReferenceOne(targetDocument="AppBundle\Document\User")
+     * @MongoDB\ReferenceOne(targetDocument="App\Document\User")
      */
     protected $sender;
 }
@@ -78,9 +78,9 @@ MessageMetadata class
 
 ```php
 <?php
-// src/AppBundle/Document/MessageMetadata.php
+// src/Document/MessageMetadata.php
 
-namespace AppBundle\Document;
+namespace App\Document;
 
 use Doctrine\ODM\MongoDB\Mapping\Annotations as ODM;
 use FOS\MessageBundle\Document\MessageMetadata as BaseMessageMetadata;
@@ -91,7 +91,7 @@ use FOS\MessageBundle\Document\MessageMetadata as BaseMessageMetadata;
 class MessageMetadata extends BaseMessageMetadata
 {
     /**
-     * @ODM\ReferenceOne(targetDocument="AppBundle\Document\User")
+     * @ODM\ReferenceOne(targetDocument="App\Document\User")
      */
     protected $participant;
 }
@@ -102,9 +102,9 @@ Thread class
 
 ```php
 <?php
-// src/AppBundle/Document/Thread.php
+// src/Document/Thread.php
 
-namespace AppBundle\Document;
+namespace App\Document;
 
 use Doctrine\ODM\MongoDB\Mapping\Annotations as MongoDB;
 use FOS\MessageBundle\Document\Thread as BaseThread;
@@ -120,22 +120,22 @@ class Thread extends BaseThread
     protected $id;
 
     /**
-     * @MongoDB\ReferenceMany(targetDocument="AppBundle\Document\Message")
+     * @MongoDB\ReferenceMany(targetDocument="App\Document\Message")
      */
     protected $messages;
 
     /**
-     * @MongoDB\EmbedMany(targetDocument="AppBundle\Document\ThreadMetadata")
+     * @MongoDB\EmbedMany(targetDocument="App\Document\ThreadMetadata")
      */
     protected $metadata;
 
     /**
-     * @MongoDB\ReferenceMany(targetDocument="AppBundle\Document\User")
+     * @MongoDB\ReferenceMany(targetDocument="App\Document\User")
      */
     protected $participants;
 
     /**
-     * @MongoDB\ReferenceOne(targetDocument="AppBundle\Document\User")
+     * @MongoDB\ReferenceOne(targetDocument="App\Document\User")
      */
     protected $createdBy;
 }
@@ -146,9 +146,9 @@ ThreadMetadata class
 
 ```php
 <?php
-// src/AppBundle/Document/ThreadMetadata.php
+// src/Document/ThreadMetadata.php
 
-namespace AppBundle\Document;
+namespace App\Document;
 
 use Doctrine\ODM\MongoDB\Mapping\Annotations as ODM;
 use FOS\MessageBundle\Document\ThreadMetadata as BaseThreadMetadata;
@@ -159,7 +159,7 @@ use FOS\MessageBundle\Document\ThreadMetadata as BaseThreadMetadata;
 class ThreadMetadata extends BaseThreadMetadata
 {
     /**
-     * @ODM\ReferenceOne(targetDocument="AppBundle\Document\User")
+     * @ODM\ReferenceOne(targetDocument="App\Document\User")
      */
     protected $participant;
 }
diff --git a/Resources/doc/04-spam-detection.md b/Resources/doc/04-spam-detection.md
index 591e5273..ce331d60 100644
--- a/Resources/doc/04-spam-detection.md
+++ b/Resources/doc/04-spam-detection.md
@@ -9,7 +9,7 @@ Install AkismetBundle (https://github.com/ornicar/OrnicarAkismetBundle).
 Then, set the spam detector service accordingly::
 
 ```yaml
-# app/config/config.yml
+# config/fos_message.yaml
 
 fos_message:
     spam_detector: fos_message.akismet_spam_detector
diff --git a/Resources/doc/05-permissions.md b/Resources/doc/05-permissions.md
index ccecc650..6d32e3c3 100644
--- a/Resources/doc/05-permissions.md
+++ b/Resources/doc/05-permissions.md
@@ -8,7 +8,7 @@ You can implement your own permissions service to replace the built in service a
 FOSMessageBundle about it:
 
 ```yaml
-# app/config/config.yml
+# config/fos_message.yaml
 
 fos_message:
     authorizer: app.authorizer
diff --git a/Resources/doc/06-events.md b/Resources/doc/06-events.md
index d9c7676d..7e19c1c4 100644
--- a/Resources/doc/06-events.md
+++ b/Resources/doc/06-events.md
@@ -1,7 +1,7 @@
 FOSMessageBundle Events
 =======================
 
-FOSMessageBundle will dispatch events inside the Symfony2 `EventDispatcher` which allows
+FOSMessageBundle will dispatch events inside the Symfony `EventDispatcher` which allows
 you to write listeners to modify or augment behaviour of the MessageBundle process.
 
 You can see definitions and explanations of each event as defined in `Event\FOSMessageEvents`:
diff --git a/Resources/doc/90-multiple-recipients.md b/Resources/doc/90-multiple-recipients.md
index d8bc1fd9..01a22a2a 100644
--- a/Resources/doc/90-multiple-recipients.md
+++ b/Resources/doc/90-multiple-recipients.md
@@ -4,12 +4,12 @@ Configuring multiple recipients support
 Configure your application
 
 ```yaml
-# app/config/config.yml
+# config/fos_message.yaml
 
 fos_message:
     db_driver: orm
-    thread_class: AppBundle\Entity\Thread
-    message_class: AppBundle\Entity\Message
+    thread_class: App\Entity\Thread
+    message_class: App\Entity\Message
     new_thread_form:
       type:               FOS\MessageBundle\FormType\NewThreadMultipleMessageFormType
       handler:            fos_message.new_thread_multiple_form.handler
diff --git a/Resources/doc/99-config-reference.md b/Resources/doc/99-config-reference.md
index b7f5a391..72e045ab 100644
--- a/Resources/doc/99-config-reference.md
+++ b/Resources/doc/99-config-reference.md
@@ -4,12 +4,12 @@ Configuration Reference
 All configuration options are listed below::
 
 ```yaml
-# app/config/config.yml
+# config/fos_message.yaml
 
 fos_message:
     db_driver:              orm
-    thread_class:           AppBundle\Entity\Thread
-    message_class:          AppBundle\Entity\Message
+    thread_class:           App\Entity\Thread
+    message_class:          App\Entity\Message
     message_manager:        fos_message.message_manager         # See ModelManager\MessageManagerInterface
     thread_manager:         fos_message.thread_manager          # See ModelManager\ThreadManagerInterface
     sender:                 fos_message.sender                  # See Sender\SenderInterface
@@ -24,8 +24,8 @@ fos_message:
     twig_extension:         fos_message.twig_extension          # See Twig\Extension\MessageExtension
     user_transformer:       fos_user.user_transformer           # See Symfony\Component\Form\DataTransformerInterface
     search:
-        finder:             fos_message.search_finder           # See Finder\FinderInterface
-        query_factory:      fos_message.search_query_factory    # See Finder\QueryFactoryInterface
+        finder:             fos_message.search.finder           # See Finder\FinderInterface
+        query_factory:      fos_message.search.query_factory    # See Finder\QueryFactoryInterface
         query_parameter:    'q'                                     # Request query parameter containing the term
     new_thread_form:
         factory:            fos_message.new_thread_form.factory # See FormFactory\NewThreadMessageFormFactory
diff --git a/Resources/doc/99-using-other-user-bundles.md b/Resources/doc/99-using-other-user-bundles.md
index 484d99d5..9d74488a 100644
--- a/Resources/doc/99-using-other-user-bundles.md
+++ b/Resources/doc/99-using-other-user-bundles.md
@@ -13,16 +13,15 @@ You can base your own on this one:
 
 ``` php
 <?php
-// src/AppBundle/Form/DataTransformer/UserToUsernameTransformer.php
 
-namespace AppBundle\Form\DataTransformer;
+namespace App\Form\DataTransformer;
 
-use Doctrine\Bundle\DoctrineBundle\Registry;
-use Doctrine\ORM\EntityRepository;
+use App\Entity\User;
+
+use Doctrine\ORM\EntityManagerInterface;
 use Symfony\Component\Form\DataTransformerInterface;
 use Symfony\Component\Form\Exception\UnexpectedTypeException;
-
-use AppBundle\Entity\User;
+use Symfony\Component\Security\Core\User\UserInterface;
 
 /**
  * Transforms between a User instance and a username string
@@ -30,60 +29,60 @@ use AppBundle\Entity\User;
 class UserToUsernameTransformer implements DataTransformerInterface
 {
     /**
-     * @var EntityRepository
+     * @var EntityManagerInterface
      */
-    protected $repository;
+    protected $em;
 
     /**
-     * @param Registry $doctrine
+     * UserToUsernameTransformer constructor.
      */
-    public function __construct(Registry $doctrine)
+    public function __construct(EntityManagerInterface $em)
     {
-        $this->repository = $doctrine->getManager()->getRepository('AppBundle:User');
+        $this->em = $em;
     }
 
     /**
-     * Transforms a User instance into a username string.
+     * Transforms a UserInterface instance into a username string.
      *
-     * @param User|null $value User instance
+     * @param UserInterface|null $value UserInterface instance
      *
      * @return string|null Username
      *
-     * @throws UnexpectedTypeException if the given value is not a User instance
+     * @throws UnexpectedTypeException if the given value is not a UserInterface instance
      */
-    public function transform($value)
+    public function transform($value): ?string
     {
         if (null === $value) {
             return null;
         }
 
-        if (! $value instanceof User) {
-            throw new UnexpectedTypeException($value, 'AppBundle\Entity\User');
+        if (!$value instanceof UserInterface) {
+            throw new UnexpectedTypeException($value, 'Symfony\Component\Security\Core\User\UserInterface');
         }
 
-        return $value->getUsername();
+        return $value->getUserIdentifier();
     }
 
     /**
-     * Transforms a username string into a User instance.
+     * Transforms a username string into a UserInterface instance.
      *
      * @param string $value Username
      *
-     * @return User the corresponding User instance
+     * @return UserInterface|null the corresponding UserInterface instance
      *
      * @throws UnexpectedTypeException if the given value is not a string
      */
-    public function reverseTransform($value)
+    public function reverseTransform($value): ?UserInterface
     {
         if (null === $value || '' === $value) {
             return null;
         }
 
-        if (! is_string($value)) {
+        if (!is_string($value)) {
             throw new UnexpectedTypeException($value, 'string');
         }
 
-        return $this->repository->findOneByUsername($value);
+        return $this->em->getRepository(User::class)->findOneByIdentifier($value);
     }
 }
 ```
@@ -93,15 +92,142 @@ For the moment, there is no configuration key to do it so we will emulate the
 FOSUserBundle transformer by using its name as an alias of our own service:
 
 ``` xml
-<!-- app/config/services.xml -->
+<!-- config/services.xml -->
 
-<service id="app.user_to_username_transformer" class="AppBundle\Form\DataTransformer\UserToUsernameTransformer">
-    <argument type="service" id="doctrine" />
+<service id="app.user_to_username_transformer" class="App\Form\DataTransformer\UserToUsernameTransformer">
 </service>
 
 <service id="fos_user.user_to_username_transformer" alias="app.user_to_username_transformer" />
 ```
 
+Or
+
+``` yaml
+# config/services.yaml
+services:
+    ...
+    app.user_to_username_transformer:
+        class: App\Form\DataTransformer\UserToUsernameTransformer
+    
+    fos_user.user_to_username_transformer:
+        alias: app.user_to_username_transformer
+```
+
+As `NewThreadMessageFormType` used `FOS\UserBundle\Form\Type\UsernameFormType` for recipied field, you need to create
+a new form type to replace it
+
+```php
+<?php
+// src/Form/Type/NewThreadMessageFormType.php
+
+namespace App\Form\Type;
+
+use App\Form\Type\UsernameFormType;
+use Symfony\Component\Form\AbstractType;
+use Symfony\Component\Form\Extension\Core\Type\TextareaType;
+use Symfony\Component\Form\Extension\Core\Type\TextType;
+use Symfony\Component\Form\FormBuilderInterface;
+use Symfony\Component\OptionsResolver\OptionsResolver;
+
+/**
+ * Message form type for starting a new conversation.
+ */
+class NewThreadMessageFormType extends AbstractType
+{
+    public function buildForm(FormBuilderInterface $builder, array $options)
+    {
+        $builder
+            ->add('recipient', UsernameFormType::class, [
+                'label' => 'recipient',
+                'translation_domain' => 'FOSMessageBundle',
+            ])
+            ->add('subject', TextType::class, [
+                'label' => 'subject',
+                'translation_domain' => 'FOSMessageBundle',
+            ])
+            ->add('body', TextareaType::class, [
+                'label' => 'body',
+                'translation_domain' => 'FOSMessageBundle',
+            ]);
+    }
+
+    public function configureOptions(OptionsResolver $resolver)
+    {
+        $resolver->setDefaults([
+            'intention' => 'message',
+        ]);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getBlockPrefix()
+    {
+        return 'new_thread_message';
+    }
+}
+```
+
+And create a new form type linked to `UserToUsernameTransformer`
+
+```php
+<?php
+// src/Form/Type/UsernameFormType.php
+
+namespace App\Form\Type;
+
+use App\Form\DataTransformer\UserToUsernameTransformer;
+use Symfony\Component\Form\Extension\Core\Type\TextType;
+use Symfony\Component\Form\AbstractType;
+use Symfony\Component\Form\FormBuilderInterface;
+
+/**
+ * Form type for representing a UserInterface instance by its username string.
+ */
+class UsernameFormType extends AbstractType
+{
+    /**
+     * @var UserToUsernameTransformer
+     */
+    protected $usernameTransformer;
+
+    /**
+     * Constructor.
+     *
+     * @param UserToUsernameTransformer $usernameTransformer
+     */
+    public function __construct(UserToUsernameTransformer $usernameTransformer)
+    {
+        $this->usernameTransformer = $usernameTransformer;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function buildForm(FormBuilderInterface $builder, array $options)
+    {
+        $builder->addModelTransformer($this->usernameTransformer);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getParent()
+    {
+        return TextType::class;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getBlockPrefix()
+    {
+        return 'app_username_type';
+    }
+}
+
+```
+
 ### Problems you may encounter
 
 #### User identifier field is not `id`
@@ -113,32 +239,31 @@ made by the bundle.
 You can copy the default ones (in `FOS\MessageBundle\EntityManager` if you use the Doctrine ORM)
 into your bundle, change their queries and register them as services:
 
-``` xml
-<!-- app/config/services.xml -->
-
-<service id="app.message_manager" class="AppBundle\EntityManager\MessageManager" public="false">
-    <argument type="service" id="doctrine.orm.entity_manager" />
-    <argument>%fos_message.message_class%</argument>
-    <argument>%fos_message.message_meta_class%</argument>
-</service>
-
-<service id="app.thread_manager" class="AppBundle\EntityManager\ThreadManager" public="false">
-    <argument type="service" id="doctrine.orm.entity_manager" />
-    <argument>%fos_message.thread_class%</argument>
-    <argument>%fos_message.thread_meta_class%</argument>
-    <argument type="service" id="app.message_manager" />
-</service>
+``` yaml
+# config/services.yaml
+
+services:
+    ...
+    App\Manager\MessageManager:
+        bind:
+            $class: '%fos_message.message_class%'
+            $metaClass: '%fos_message.message_meta_class%'
+
+    App\Manager\ThreadManager:
+        bind:
+            $class: '%fos_message.thread_class%'
+            $metaClass: '%fos_message.thread_meta_class%'
 ```
 
 Once done, tell FOSMessageBundle to use them in the configuration:
 
 ``` yaml
-# app/config/config.yml
+# config/fos_message.yaml
 
 fos_message:
 	# ...
-    thread_manager: app.thread_manager
-    message_manager: app.message_manager
+    thread_manager: App\Manager\ThreadManager
+    message_manager: App\Manager\MessageManager
 ```
 
 #### The default form does not work with my User entity
@@ -150,11 +275,11 @@ You have to redefine two things :
 You can copy and paste the bundle versions into your application and define them as services:
 
 ``` xml
-<service id="app.new_thread_form_type" class="AppBundle\Form\NewThreadMessageFormType" public="false">
+<service id="app.new_thread_form_type" class="App\Form\NewThreadMessageFormType" public="false">
     <argument type="service" id="app.user_to_username_transformer" />
 </service>
 
-<service id="app.new_thread_form_factory" class="AppBundle\Form\NewThreadMessageFormFactory" public="false">
+<service id="app.new_thread_form_factory" class="App\Form\NewThreadMessageFormFactory" public="false">
     <argument type="service" id="form.factory" />
     <argument type="service" id="fos_message.new_thread_form.type" />
     <argument>%fos_message.new_thread_form.name%</argument>
@@ -167,7 +292,7 @@ You can copy and paste the bundle versions into your application and define them
 And configure the bundle to use your services:
 
 ``` yaml
-# app/config/config.yml
+# config/fos_message.yaml
 
 fos_message:
     # ...
diff --git a/Sender/Sender.php b/Sender/Sender.php
index 471d44f2..7201fd43 100644
--- a/Sender/Sender.php
+++ b/Sender/Sender.php
@@ -31,8 +31,11 @@ class Sender implements SenderInterface
      */
     protected $dispatcher;
 
-    public function __construct(MessageManagerInterface $messageManager, ThreadManagerInterface $threadManager, EventDispatcherInterface $dispatcher)
-    {
+    public function __construct(
+        MessageManagerInterface $messageManager,
+        ThreadManagerInterface $threadManager,
+        EventDispatcherInterface $dispatcher
+    ) {
         $this->messageManager = $messageManager;
         $this->threadManager = $threadManager;
         $this->dispatcher = $dispatcher;
@@ -54,6 +57,6 @@ public function send(MessageInterface $message)
         $message->getThread()->setIsDeleted(false);
         $this->messageManager->saveMessage($message);
 
-        $this->dispatcher->dispatch(FOSMessageEvents::POST_SEND, new MessageEvent($message));
+        $this->dispatcher->dispatch(new MessageEvent($message), FOSMessageEvents::POST_SEND);
     }
 }
diff --git a/SpamDetection/AkismetSpamDetector.php b/SpamDetection/AkismetSpamDetector.php
index 070d8160..3ef54208 100644
--- a/SpamDetection/AkismetSpamDetector.php
+++ b/SpamDetection/AkismetSpamDetector.php
@@ -29,9 +29,9 @@ public function __construct(AkismetInterface $akismet, ParticipantProviderInterf
      */
     public function isSpam(NewThreadMessage $message)
     {
-        return $this->akismet->isSpam(array(
+        return $this->akismet->isSpam([
             'comment_author' => (string) $this->participantProvider->getAuthenticatedParticipant(),
-            'comment_content' => $message->getBody(),
-        ));
+            'comment_content' => $message->getBody()
+        ]);
     }
 }
diff --git a/Tests/Document/ThreadDenormalizerTest.php b/Tests/Document/ThreadDenormalizerTest.php
index 0196b206..81902f5d 100644
--- a/Tests/Document/ThreadDenormalizerTest.php
+++ b/Tests/Document/ThreadDenormalizerTest.php
@@ -20,12 +20,12 @@ protected function setUpBeforeTest()
     {
         $this->markTestIncomplete('Broken, needs to be fixed');
 
-        $this->dates = array(
+        $this->dates = [
             new DateTime('- 3 days'),
             new DateTime('- 2 days'),
             new DateTime('- 1 days'),
-            new DateTime('- 1 hour'),
-        );
+            new DateTime('- 1 hour')
+        ];
     }
 
     public function testDenormalize()
@@ -44,9 +44,9 @@ public function testDenormalize()
         $thread->addParticipant($user2);
         $thread->addMessage($message);
 
-        $this->assertSame(array($user1, $user2), $thread->getParticipants());
-        $this->assertSame(array('u2' => $this->dates[0]->getTimestamp()), $thread->getDatesOfLastMessageWrittenByOtherParticipant());
-        $this->assertSame(array('u1' => $this->dates[0]->getTimestamp()), $thread->getDatesOfLastMessageWrittenByParticipant());
+        $this->assertSame([$user1, $user2], $thread->getParticipants());
+        $this->assertSame(['u2' => $this->dates[0]->getTimestamp()], $thread->getDatesOfLastMessageWrittenByOtherParticipant());
+        $this->assertSame(['u1' => $this->dates[0]->getTimestamp()], $thread->getDatesOfLastMessageWrittenByParticipant());
 
         /*
          * Second message
@@ -54,9 +54,9 @@ public function testDenormalize()
         $message = $this->createMessageMock($user2, $user1, $this->dates[1]);
         $thread->addMessage($message);
 
-        $this->assertSame(array($user1, $user2), $thread->getParticipants());
-        $this->assertSame(array('u1' => $this->dates[1]->getTimestamp(), 'u2' => $this->dates[0]->getTimestamp()), $thread->getDatesOfLastMessageWrittenByOtherParticipant());
-        $this->assertSame(array('u1' => $this->dates[0]->getTimestamp(), 'u2' => $this->dates[1]->getTimestamp()), $thread->getDatesOfLastMessageWrittenByParticipant());
+        $this->assertSame([$user1, $user2], $thread->getParticipants());
+        $this->assertSame(['u1' => $this->dates[1]->getTimestamp(), 'u2' => $this->dates[0]->getTimestamp()], $thread->getDatesOfLastMessageWrittenByOtherParticipant());
+        $this->assertSame(['u1' => $this->dates[0]->getTimestamp(), 'u2' => $this->dates[1]->getTimestamp()], $thread->getDatesOfLastMessageWrittenByParticipant());
 
         /*
          * Third message
@@ -64,9 +64,9 @@ public function testDenormalize()
         $message = $this->createMessageMock($user2, $user1, $this->dates[2]);
         $thread->addMessage($message);
 
-        $this->assertSame(array($user1, $user2), $thread->getParticipants());
-        $this->assertSame(array('u1' => $this->dates[2]->getTimestamp(), 'u2' => $this->dates[0]->getTimestamp()), $thread->getDatesOfLastMessageWrittenByOtherParticipant());
-        $this->assertSame(array('u1' => $this->dates[0]->getTimestamp(), 'u2' => $this->dates[2]->getTimestamp()), $thread->getDatesOfLastMessageWrittenByParticipant());
+        $this->assertSame([$user1, $user2], $thread->getParticipants());
+        $this->assertSame(['u1' => $this->dates[2]->getTimestamp(), 'u2' => $this->dates[0]->getTimestamp()], $thread->getDatesOfLastMessageWrittenByOtherParticipant());
+        $this->assertSame(['u1' => $this->dates[0]->getTimestamp(), 'u2' => $this->dates[2]->getTimestamp()], $thread->getDatesOfLastMessageWrittenByParticipant());
 
         /*
          * Fourth message
@@ -74,12 +74,12 @@ public function testDenormalize()
         $message = $this->createMessageMock($user1, $user2, $this->dates[3]);
         $thread->addMessage($message);
 
-        $this->assertSame(array($user1, $user2), $thread->getParticipants());
-        $this->assertSame(array('u1' => $this->dates[2]->getTimestamp(), 'u2' => $this->dates[3]->getTimestamp()), $thread->getDatesOfLastMessageWrittenByOtherParticipant());
-        $this->assertSame(array('u1' => $this->dates[3]->getTimestamp(), 'u2' => $this->dates[2]->getTimestamp()), $thread->getDatesOfLastMessageWrittenByParticipant());
+        $this->assertSame([$user1, $user2], $thread->getParticipants());
+        $this->assertSame(['u1' => $this->dates[2]->getTimestamp(), 'u2' => $this->dates[3]->getTimestamp()], $thread->getDatesOfLastMessageWrittenByOtherParticipant());
+        $this->assertSame(['u1' => $this->dates[3]->getTimestamp(), 'u2' => $this->dates[2]->getTimestamp()], $thread->getDatesOfLastMessageWrittenByParticipant());
 
         $this->assertEquals('test thread subject hi dude', $thread->getKeywords());
-        $this->assertSame(array('u1' => false, 'u2' => false), $thread->getIsDeletedByParticipant());
+        $this->assertSame(['u1' => false, 'u2' => false], $thread->getIsDeletedByParticipant());
     }
 
     protected function createMessageMock($sender, $recipient, DateTime $date)
diff --git a/Tests/Functional/Entity/Message.php b/Tests/Functional/Entity/Message.php
index de629e15..9e9c97d4 100644
--- a/Tests/Functional/Entity/Message.php
+++ b/Tests/Functional/Entity/Message.php
@@ -4,6 +4,40 @@
 
 use FOS\MessageBundle\Entity\Message as BaseMessage;
 
+/**
+ * @ORM\Entity
+ */
 class Message extends BaseMessage
 {
+    /**
+     * @ORM\Id
+     * @ORM\Column(type="integer")
+     * @ORM\GeneratedValue(strategy="AUTO")
+     */
+    protected $id;
+
+    /**
+     * @ORM\ManyToOne(
+     *   targetEntity="App\Entity\Thread",
+     *   inversedBy="messages"
+     * )
+     * @var \FOS\MessageBundle\Model\ThreadInterface
+     */
+    protected $thread;
+
+    /**
+     * @ORM\ManyToOne(targetEntity="App\Entity\User")
+     * @var \FOS\MessageBundle\Model\ParticipantInterface
+     */
+    protected $sender;
+
+    /**
+     * @ORM\OneToMany(
+     *   targetEntity="App\Entity\MessageMetadata",
+     *   mappedBy="message",
+     *   cascade={"all"}
+     * )
+     * @var MessageMetadata[]|Collection
+     */
+    protected $metadata;
 }
diff --git a/Tests/Functional/Entity/User.php b/Tests/Functional/Entity/User.php
index 5ebbe971..135b7974 100644
--- a/Tests/Functional/Entity/User.php
+++ b/Tests/Functional/Entity/User.php
@@ -3,16 +3,17 @@
 namespace FOS\MessageBundle\Tests\Functional\Entity;
 
 use FOS\MessageBundle\Model\ParticipantInterface;
+use Symfony\Component\Security\Core\User\PasswordAuthenticatedUserInterface;
 use Symfony\Component\Security\Core\User\UserInterface;
 
-class User implements ParticipantInterface, UserInterface
+class User implements ParticipantInterface, UserInterface, PasswordAuthenticatedUserInterface
 {
-    public function getUsername()
+    public function getUserIdentifier(): string
     {
         return 'guilhem';
     }
 
-    public function getPassword()
+    public function getPassword(): ?string
     {
         return 'pass';
     }
@@ -21,9 +22,9 @@ public function getSalt()
     {
     }
 
-    public function getRoles()
+    public function getRoles(): array
     {
-        return array();
+        return [];
     }
 
     public function eraseCredentials()
@@ -34,4 +35,14 @@ public function getId()
     {
         return 1;
     }
+
+    public function getUserName(): string
+    {
+        return $this->getUserIdentifier();
+    }
+
+    public function __toString(): string
+    {
+        return $this->getUserIdentifier();
+    }
 }
diff --git a/Tests/Functional/Entity/UserProvider.php b/Tests/Functional/Entity/UserProvider.php
index 704995d7..1b3658e4 100644
--- a/Tests/Functional/Entity/UserProvider.php
+++ b/Tests/Functional/Entity/UserProvider.php
@@ -7,17 +7,17 @@
 
 class UserProvider implements UserProviderInterface
 {
-    public function loadUserByUsername($username)
+    public function loadUserByIdentifier($username): UserInterface
     {
         return new User();
     }
 
-    public function refreshUser(UserInterface $user)
+    public function refreshUser(UserInterface $user): UserInterface
     {
         return $user;
     }
 
-    public function supportsClass($class)
+    public function supportsClass($class): bool
     {
         return User::class === $class;
     }
@@ -26,4 +26,9 @@ private function fetchUser($username)
     {
         return new User();
     }
+
+    public function loadUserByUsername($username): UserInterface
+    {
+        return $this->loadUserByIdentifier($username);
+    }
 }
diff --git a/Tests/Functional/EntityManager/ThreadManager.php b/Tests/Functional/EntityManager/ThreadManager.php
index fa03ef74..aed6f0b2 100644
--- a/Tests/Functional/EntityManager/ThreadManager.php
+++ b/Tests/Functional/EntityManager/ThreadManager.php
@@ -21,7 +21,7 @@ public function getParticipantInboxThreadsQueryBuilder(ParticipantInterface $par
 
     public function findParticipantInboxThreads(ParticipantInterface $participant)
     {
-        return array(new Thread());
+        return [new Thread()];
     }
 
     public function getParticipantSentThreadsQueryBuilder(ParticipantInterface $participant)
@@ -30,7 +30,7 @@ public function getParticipantSentThreadsQueryBuilder(ParticipantInterface $part
 
     public function findParticipantSentThreads(ParticipantInterface $participant)
     {
-        return array();
+        return [];
     }
 
     public function getParticipantDeletedThreadsQueryBuilder(ParticipantInterface $participant)
@@ -39,7 +39,7 @@ public function getParticipantDeletedThreadsQueryBuilder(ParticipantInterface $p
 
     public function findParticipantDeletedThreads(ParticipantInterface $participant)
     {
-        return array();
+        return [];
     }
 
     public function getParticipantThreadsBySearchQueryBuilder(ParticipantInterface $participant, $search)
@@ -48,12 +48,12 @@ public function getParticipantThreadsBySearchQueryBuilder(ParticipantInterface $
 
     public function findParticipantThreadsBySearch(ParticipantInterface $participant, $search)
     {
-        return array();
+        return [];
     }
 
     public function findThreadsCreatedBy(ParticipantInterface $participant)
     {
-        return array();
+        return [];
     }
 
     public function markAsReadByParticipant(ReadableInterface $readable, ParticipantInterface $participant)
diff --git a/Tests/Functional/Form/UserToUsernameTransformer.php b/Tests/Functional/Form/UserToUsernameTransformer.php
index 915ab171..4e123863 100644
--- a/Tests/Functional/Form/UserToUsernameTransformer.php
+++ b/Tests/Functional/Form/UserToUsernameTransformer.php
@@ -8,17 +8,17 @@
 
 class UserToUsernameTransformer implements DataTransformerInterface
 {
-    public function transform($value)
+    public function transform($value): ?string
     {
         if (null === $value) {
-            return;
+            return null;
         }
 
         if (!$value instanceof User) {
             throw new \RuntimeException();
         }
 
-        return $value->getUsername();
+        return $value->getUserIdentifier();
     }
 
     /**
diff --git a/Tests/Functional/FunctionalTest.php b/Tests/Functional/FunctionalTest.php
index bd0dffcc..c4b3e4eb 100644
--- a/Tests/Functional/FunctionalTest.php
+++ b/Tests/Functional/FunctionalTest.php
@@ -6,10 +6,7 @@ class FunctionalTest extends WebTestCase
 {
     public function testController()
     {
-        $client = self::createClient(array(), array(
-            'PHP_AUTH_USER' => 'guilhem',
-            'PHP_AUTH_PW' => 'pass',
-        ));
+        $client = self::createClient([], ['PHP_AUTH_USER' => 'guilhem', 'PHP_AUTH_PW' => 'pass']);
         $crawler = $client->request('GET', '/sent');
 
         $response = $client->getResponse();
diff --git a/Tests/Functional/TestKernel.php b/Tests/Functional/TestKernel.php
index 22f04dc9..8ca97425 100644
--- a/Tests/Functional/TestKernel.php
+++ b/Tests/Functional/TestKernel.php
@@ -17,7 +17,7 @@
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\HttpKernel\Kernel;
-use Symfony\Component\Routing\RouteCollectionBuilder;
+use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;
 
 /**
  * @author Guilhem N. <guilhem.niot@gmail.com>
@@ -29,14 +29,14 @@ class TestKernel extends Kernel
     /**
      * {@inheritdoc}
      */
-    public function registerBundles()
+    public function registerBundles(): iterable
     {
-        $bundles = array(
+        $bundles = [
             new FrameworkBundle(),
             new SecurityBundle(),
             new TwigBundle(),
             new FOSMessageBundle(),
-        );
+        ];
 
         return $bundles;
     }
@@ -44,7 +44,7 @@ public function registerBundles()
     /**
      * {@inheritdoc}
      */
-    protected function configureRoutes(RouteCollectionBuilder $routes)
+    protected function configureRoutes(RoutingConfigurator $routes)
     {
         $routes->import('@FOSMessageBundle/Resources/config/routing.xml');
     }
@@ -54,30 +54,28 @@ protected function configureRoutes(RouteCollectionBuilder $routes)
      */
     protected function configureContainer(ContainerBuilder $c, LoaderInterface $loader)
     {
-        $c->loadFromExtension('framework', array(
+        $c->loadFromExtension('framework', [
             'secret' => 'MySecretKey',
             'test' => null,
             'form' => null,
-            'templating' => array(
-                'engines' => array('twig'),
-            ),
-        ));
+            'http_method_override' => false
+        ]);
 
-        $c->loadFromExtension('security', array(
-            'providers' => array('permissive' => array('id' => 'app.user_provider')),
-            'encoders' => array('FOS\MessageBundle\Tests\Functional\Entity\User' => 'plaintext'),
-            'firewalls' => array('main' => array('http_basic' => true)),
-        ));
+        $c->loadFromExtension('security', [
+            'providers' => ['permissive' => ['id' => 'app.user_provider']],
+            'password_hashers' => ['FOS\MessageBundle\Tests\Functional\Entity\User' => 'plaintext'],
+            'firewalls' => ['main' => ['http_basic' => true]],
+        ]);
 
-        $c->loadFromExtension('twig', array(
+        $c->loadFromExtension('twig', [
             'strict_variables' => '%kernel.debug%',
-        ));
+        ]);
 
-        $c->loadFromExtension('fos_message', array(
+        $c->loadFromExtension('fos_message', [
             'db_driver' => 'orm',
             'thread_class' => Thread::class,
             'message_class' => Message::class,
-        ));
+        ]);
 
         $c->register('fos_user.user_to_username_transformer', UserToUsernameTransformer::class);
         $c->register('app.user_provider', UserProvider::class);
diff --git a/Tests/Functional/WebTestCase.php b/Tests/Functional/WebTestCase.php
index e853eed5..8364df2c 100644
--- a/Tests/Functional/WebTestCase.php
+++ b/Tests/Functional/WebTestCase.php
@@ -6,7 +6,7 @@
 
 class WebTestCase extends BaseWebTestCase
 {
-    protected static function getKernelClass()
+    protected static function getKernelClass(): string
     {
         return 'FOS\MessageBundle\Tests\Functional\TestKernel';
     }
diff --git a/Tests/Model/ThreadTest.php b/Tests/Model/ThreadTest.php
index d1eb8d01..b006c5d7 100644
--- a/Tests/Model/ThreadTest.php
+++ b/Tests/Model/ThreadTest.php
@@ -16,7 +16,7 @@ public function testGetOtherParticipants()
         $thread = $this->getMockForAbstractClass('FOS\MessageBundle\Model\Thread');
         $thread->expects($this->atLeastOnce())
             ->method('getParticipants')
-            ->will($this->returnValue(array($u1, $u2, $u3)));
+            ->will($this->returnValue([$u1, $u2, $u3]));
 
         $toIds = function (array $participants) {
             return array_map(function (ParticipantInterface $participant) {
@@ -24,9 +24,9 @@ public function testGetOtherParticipants()
             }, $participants);
         };
 
-        $this->assertSame($toIds(array($u2, $u3)), $toIds($thread->getOtherParticipants($u1)));
-        $this->assertSame($toIds(array($u1, $u3)), $toIds($thread->getOtherParticipants($u2)));
-        $this->assertSame($toIds(array($u1, $u2)), $toIds($thread->getOtherParticipants($u3)));
+        $this->assertSame($toIds([$u2, $u3]), $toIds($thread->getOtherParticipants($u1)));
+        $this->assertSame($toIds([$u1, $u3]), $toIds($thread->getOtherParticipants($u2)));
+        $this->assertSame($toIds([$u1, $u2]), $toIds($thread->getOtherParticipants($u3)));
     }
 
     protected function createParticipantMock($id)
diff --git a/Tests/Twig/Extension/MessageExtensionTest.php b/Tests/Twig/Extension/MessageExtensionTest.php
index 85597bc8..2f8ab94d 100644
--- a/Tests/Twig/Extension/MessageExtensionTest.php
+++ b/Tests/Twig/Extension/MessageExtensionTest.php
@@ -2,7 +2,7 @@
 
 namespace FOS\MessageBundle\Tests\Twig\Extension;
 
-use FOS\MessageBundle\Twig\Extension\MessageExtension;
+use FOS\MessageBundle\Twig\MessageExtension;
 use PHPUnit\Framework\TestCase;
 
 /**
diff --git a/Twig/Extension/MessageExtension.php b/Twig/MessageExtension.php
similarity index 81%
rename from Twig/Extension/MessageExtension.php
rename to Twig/MessageExtension.php
index dba25a4c..08ae9cca 100644
--- a/Twig/Extension/MessageExtension.php
+++ b/Twig/MessageExtension.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace FOS\MessageBundle\Twig\Extension;
+namespace FOS\MessageBundle\Twig;
 
 use FOS\MessageBundle\Model\ParticipantInterface;
 use FOS\MessageBundle\Model\ReadableInterface;
@@ -19,8 +19,11 @@ class MessageExtension extends AbstractExtension
 
     protected $nbUnreadMessagesCache;
 
-    public function __construct(ParticipantProviderInterface $participantProvider, ProviderInterface $provider, AuthorizerInterface $authorizer)
-    {
+    public function __construct(
+        ParticipantProviderInterface $participantProvider,
+        ProviderInterface $provider,
+        AuthorizerInterface $authorizer
+    ) {
         $this->participantProvider = $participantProvider;
         $this->provider = $provider;
         $this->authorizer = $authorizer;
@@ -29,14 +32,14 @@ public function __construct(ParticipantProviderInterface $participantProvider, P
     /**
      * {@inheritdoc}
      */
-    public function getFunctions()
+    public function getFunctions(): array
     {
-        return array(
-            new TwigFunction('fos_message_is_read', array($this, 'isRead')),
-            new TwigFunction('fos_message_nb_unread', array($this, 'getNbUnread')),
-            new TwigFunction('fos_message_can_delete_thread', array($this, 'canDeleteThread')),
-            new TwigFunction('fos_message_deleted_by_participant', array($this, 'isThreadDeletedByParticipant')),
-        );
+        return [
+            new TwigFunction('fos_message_is_read', [$this, 'isRead']),
+            new TwigFunction('fos_message_nb_unread', [$this, 'getNbUnread']),
+            new TwigFunction('fos_message_can_delete_thread', [$this, 'canDeleteThread']),
+            new TwigFunction('fos_message_deleted_by_participant', [$this, 'isThreadDeletedByParticipant'])
+        ];
     }
 
     /**
diff --git a/UPGRADING.md b/UPGRADING.md
index 74a9257a..4751a69d 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -30,7 +30,7 @@ The 1.3 version added the support for Symfony 3.0+. Several changes were made fo
        # ...
        
        new_thread_form:
-           type: AppBundle\Form\Type\NewThreadFormType
+           type: App\Form\Type\NewThreadFormType
        reply_form:
-           type: AppBundle\Form\Type\ReplyFormType
+           type: App\Form\Type\ReplyFormType
    ```
diff --git a/Util/LegacyFormHelper.php b/Util/LegacyFormHelper.php
index 54cc5bf5..171aaa92 100644
--- a/Util/LegacyFormHelper.php
+++ b/Util/LegacyFormHelper.php
@@ -11,15 +11,15 @@
  */
 final class LegacyFormHelper
 {
-    private static $map = array(
+    private static $map = [
         'FOS\UserBundle\Form\Type\UsernameFormType' => 'fos_user_username',
         'FOS\MessageBundle\FormType\RecipientsType' => 'recipients_selector',
         'Symfony\Component\Form\Extension\Core\Type\EmailType' => 'email',
         'Symfony\Component\Form\Extension\Core\Type\PasswordType' => 'password',
         'Symfony\Component\Form\Extension\Core\Type\RepeatedType' => 'repeated',
         'Symfony\Component\Form\Extension\Core\Type\TextType' => 'text',
-        'Symfony\Component\Form\Extension\Core\Type\TextareaType' => 'textarea',
-    );
+        'Symfony\Component\Form\Extension\Core\Type\TextareaType' => 'textarea'
+    ];
 
     public static function getType($class)
     {
diff --git a/composer.json b/composer.json
index 493bd5f7..b9fe3136 100644
--- a/composer.json
+++ b/composer.json
@@ -17,21 +17,22 @@
         }
     ],
     "require": {
-        "php": ">=5.5.9",
+        "php": ">=7.2",
         "doctrine/collections": "^1.3",
-        "symfony/form": "^3.4|^4.0",
-        "symfony/framework-bundle": "^3.4|^4.0",
-        "symfony/security": "^3.4|^4.0",
-        "symfony/twig-bundle": "^3.4|^4.0"
+        "symfony/event-dispatcher": "^5.0 || ^6.0",
+        "symfony/event-dispatcher-contracts": "^2.0 || ^3.0",
+        "symfony/form": "^5.0|^6.0",
+        "symfony/framework-bundle": "^5.0|^6.0",
+        "symfony/security-bundle": "^5.0|^6.0",
+        "symfony/twig-bundle": "^5.0|^6.0"
     },
     "require-dev": {
-        "symfony/validator": "^3.4|^4.0",
-        "symfony/translation": "^3.4|^4.0",
-        "symfony/yaml": "^3.4|^4.0",
-        "symfony/security-bundle": "^3.4|^4.0",
-        "symfony/templating": "^3.4|^4.0",
-        "symfony/browser-kit": "^3.4|^4.0",
-        "symfony/phpunit-bridge": "^4.2.8",
+        "symfony/validator": "^5.0|^6.0",
+        "symfony/translation": "^5.0|^6.0",
+        "symfony/yaml": "^5.0|^6.0",
+        "symfony/security-bundle": "^5.0|^6.0",
+        "symfony/browser-kit": "^5.0|^6.0",
+        "symfony/phpunit-bridge": "^6.1",
         "doctrine/orm": "^2.0"
     },
     "suggest": {