diff --git a/src/Command/AddUserCommand.php b/src/Command/AddUserCommand.php
index fb8169408..1456766a8 100644
--- a/src/Command/AddUserCommand.php
+++ b/src/Command/AddUserCommand.php
@@ -199,7 +199,7 @@ protected function execute(InputInterface $input, OutputInterface $output)
 
         $event = $stopwatch->stop('add-user-command');
         if ($output->isVerbose()) {
-            $this->io->comment(sprintf('New user database id: %d / Elapsed time: %.2f ms / Consumed memory: %.2f MB', $user->getId(), $event->getDuration(), $event->getMemory() / pow(1024, 2)));
+            $this->io->comment(sprintf('New user database id: %d / Elapsed time: %.2f ms / Consumed memory: %.2f MB', $user->getId(), $event->getDuration(), $event->getMemory() / (1024 ** 2)));
         }
     }
 
diff --git a/src/DataFixtures/FixturesTrait.php b/src/DataFixtures/FixturesTrait.php
index 16ecdf0f2..334aed0dc 100644
--- a/src/DataFixtures/FixturesTrait.php
+++ b/src/DataFixtures/FixturesTrait.php
@@ -123,7 +123,7 @@ private function getRandomPostSummary(int $maxLength = 255): string
     {
         $phrases = $this->getPhrases();
 
-        $numPhrases = mt_rand(6, 12);
+        $numPhrases = random_int(6, 12);
         shuffle($phrases);
         $phrases = array_slice($phrases, 0, $numPhrases - 1);
 
@@ -138,7 +138,7 @@ private function getRandomCommentContent(): string
     {
         $phrases = $this->getPhrases();
 
-        $numPhrases = mt_rand(2, 15);
+        $numPhrases = random_int(2, 15);
         shuffle($phrases);
 
         return implode(' ', array_slice($phrases, 0, $numPhrases - 1));
diff --git a/src/DataFixtures/ORM/PostFixtures.php b/src/DataFixtures/ORM/PostFixtures.php
index d0d16cc5f..29b147e9c 100644
--- a/src/DataFixtures/ORM/PostFixtures.php
+++ b/src/DataFixtures/ORM/PostFixtures.php
@@ -57,7 +57,7 @@ public function load(ObjectManager $manager): void
             $post->setAuthor(0 === $i ? $this->getReference('jane-admin') : $this->getRandomUser());
 
             // for aesthetic reasons, the first blog post always has 2 tags
-            foreach ($this->getRandomTags($i > 0 ? mt_rand(0, 3) : 2) as $tag) {
+            foreach ($this->getRandomTags($i > 0 ? random_int(0, 3) : 2) as $tag) {
                 $post->addTag($tag);
             }
 
diff --git a/src/Entity/User.php b/src/Entity/User.php
index 42e5da350..a2f36c33b 100644
--- a/src/Entity/User.php
+++ b/src/Entity/User.php
@@ -168,13 +168,8 @@ public function eraseCredentials(): void
      */
     public function serialize(): string
     {
-        return serialize([
-            $this->id,
-            $this->username,
-            $this->password,
-            // see section on salt below
-            // $this->salt,
-        ]);
+        // add $this->salt too if you don't use Bcrypt or Argon2i
+        return serialize([$this->id, $this->username, $this->password]);
     }
 
     /**
@@ -182,12 +177,7 @@ public function serialize(): string
      */
     public function unserialize($serialized): void
     {
-        list(
-            $this->id,
-            $this->username,
-            $this->password,
-            // see section on salt below
-            // $this->salt
-        ) = unserialize($serialized);
+        // add $this->salt too if you don't use Bcrypt or Argon2i
+        [$this->id, $this->username, $this->password] = unserialize($serialized, ['allowed_classes' => false]);
     }
 }
diff --git a/src/EventSubscriber/RedirectToPreferredLocaleSubscriber.php b/src/EventSubscriber/RedirectToPreferredLocaleSubscriber.php
index 7684bc588..477359d1e 100644
--- a/src/EventSubscriber/RedirectToPreferredLocaleSubscriber.php
+++ b/src/EventSubscriber/RedirectToPreferredLocaleSubscriber.php
@@ -28,8 +28,8 @@
 class RedirectToPreferredLocaleSubscriber implements EventSubscriberInterface
 {
     private $urlGenerator;
-    private $locales = [];
-    private $defaultLocale = '';
+    private $locales;
+    private $defaultLocale;
 
     public function __construct(UrlGeneratorInterface $urlGenerator, string $locales, string $defaultLocale = null)
     {
diff --git a/src/Form/Type/DateTimePickerType.php b/src/Form/Type/DateTimePickerType.php
index dea737747..1ae608b60 100644
--- a/src/Form/Type/DateTimePickerType.php
+++ b/src/Form/Type/DateTimePickerType.php
@@ -41,7 +41,7 @@ public function __construct(MomentFormatConverter $converter)
     public function buildView(FormView $view, FormInterface $form, array $options)
     {
         $view->vars['attr']['data-date-format'] = $this->formatConverter->convert($options['format']);
-        $view->vars['attr']['data-date-locale'] = mb_strtolower(strtr(\Locale::getDefault(), '_', '-'));
+        $view->vars['attr']['data-date-locale'] = mb_strtolower(str_replace('_', '-', \Locale::getDefault()));
     }
 
     /**
diff --git a/tests/Form/DataTransformer/TagArrayToStringTransformerTest.php b/tests/Form/DataTransformer/TagArrayToStringTransformerTest.php
index 704536f1e..290242cb7 100644
--- a/tests/Form/DataTransformer/TagArrayToStringTransformerTest.php
+++ b/tests/Form/DataTransformer/TagArrayToStringTransformerTest.php
@@ -106,7 +106,7 @@ public function testTransform()
      *
      * @return TagArrayToStringTransformer
      */
-    private function getMockedTransformer($findByReturnValues = [])
+    private function getMockedTransformer(array $findByReturnValues = []): TagArrayToStringTransformer
     {
         $tagRepository = $this->getMockBuilder(EntityRepository::class)
             ->disableOriginalConstructor()
@@ -133,7 +133,7 @@ private function getMockedTransformer($findByReturnValues = [])
      *
      * @return Tag
      */
-    private function createTag($name)
+    private function createTag($name): Tag
     {
         $tag = new Tag();
         $tag->setName($name);