diff --git a/src/Doctrine/Functions/Field2.php b/src/Doctrine/Functions/Field2.php
index dc12b294..2e11a855 100644
--- a/src/Doctrine/Functions/Field2.php
+++ b/src/Doctrine/Functions/Field2.php
@@ -36,7 +36,7 @@ class Field2 extends FunctionNode
 
     private $values = [];
 
-    public function parse(\Doctrine\ORM\Query\Parser $parser)
+    public function parse(\Doctrine\ORM\Query\Parser $parser): void
     {
         $parser->match(Lexer::T_IDENTIFIER);
         $parser->match(Lexer::T_OPEN_PARENTHESIS);
@@ -58,7 +58,7 @@ class Field2 extends FunctionNode
         $parser->match(Lexer::T_CLOSE_PARENTHESIS);
     }
 
-    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker)
+    public function getSql(\Doctrine\ORM\Query\SqlWalker $sqlWalker): string
     {
         $query = 'FIELD2(';
 
diff --git a/src/Entity/OAuthToken.php b/src/Entity/OAuthToken.php
index b1534a4d..3924e1a8 100644
--- a/src/Entity/OAuthToken.php
+++ b/src/Entity/OAuthToken.php
@@ -135,17 +135,17 @@ class OAuthToken extends AbstractNamedDBElement implements AccessTokenInterface
         $this->expires_at = self::unixTimestampToDatetime($accessToken->getExpires() ?? time() + self::DEFAULT_EXPIRATION_TIME);
     }
 
-    public function getExpires()
+    public function getExpires(): ?int
     {
         return $this->expires_at->getTimestamp();
     }
 
-    public function hasExpired()
+    public function hasExpired(): bool
     {
         return $this->isExpired();
     }
 
-    public function getValues()
+    public function getValues(): array
     {
         return [];
     }
diff --git a/src/EventSubscriber/SwitchUserEventSubscriber.php b/src/EventSubscriber/SwitchUserEventSubscriber.php
index a7f2e39c..b68f6b4f 100644
--- a/src/EventSubscriber/SwitchUserEventSubscriber.php
+++ b/src/EventSubscriber/SwitchUserEventSubscriber.php
@@ -38,7 +38,7 @@ class SwitchUserEventSubscriber implements EventSubscriberInterface
     {
     }
 
-    public static function getSubscribedEvents()
+    public static function getSubscribedEvents(): array
     {
         return [
             'security.switch_user' => 'onSwitchUser',
diff --git a/src/Form/InfoProviderSystem/ProviderSelectType.php b/src/Form/InfoProviderSystem/ProviderSelectType.php
index 6ebe663d..26ff6be9 100644
--- a/src/Form/InfoProviderSystem/ProviderSelectType.php
+++ b/src/Form/InfoProviderSystem/ProviderSelectType.php
@@ -43,7 +43,7 @@ class ProviderSelectType extends AbstractType
         return ChoiceType::class;
     }
 
-    public function configureOptions(OptionsResolver $resolver)
+    public function configureOptions(OptionsResolver $resolver): void
     {
         $resolver->setDefaults([
             'choices' => $this->providerRegistry->getActiveProviders(),
diff --git a/src/Form/PasswordTypeExtension.php b/src/Form/PasswordTypeExtension.php
index f97eeb8e..a911bf90 100644
--- a/src/Form/PasswordTypeExtension.php
+++ b/src/Form/PasswordTypeExtension.php
@@ -46,7 +46,7 @@ class PasswordTypeExtension extends AbstractTypeExtension
         $resolver->setAllowedTypes('password_estimator', 'bool');
     }
 
-    public function finishView(FormView $view, FormInterface $form, array $options)
+    public function finishView(FormView $view, FormInterface $form, array $options): void
     {
         $view->vars['password_estimator'] = $options['password_estimator'];
     }
diff --git a/src/Form/ProjectSystem/ProjectAddPartsType.php b/src/Form/ProjectSystem/ProjectAddPartsType.php
index f89f3567..ddcdc33a 100644
--- a/src/Form/ProjectSystem/ProjectAddPartsType.php
+++ b/src/Form/ProjectSystem/ProjectAddPartsType.php
@@ -35,7 +35,7 @@ use Symfony\Component\Validator\Constraints\NotNull;
 
 class ProjectAddPartsType extends AbstractType
 {
-    public function buildForm(FormBuilderInterface $builder, array $options)
+    public function buildForm(FormBuilderInterface $builder, array $options): void
     {
         $builder->add('project', StructuralEntityType::class, [
             'class' => Project::class,
@@ -73,7 +73,7 @@ class ProjectAddPartsType extends AbstractType
         });
     }
 
-    public function configureOptions(OptionsResolver $resolver)
+    public function configureOptions(OptionsResolver $resolver): void
     {
         $resolver->setDefaults([
             'project' => null,
diff --git a/src/Serializer/AttachmentNormalizer.php b/src/Serializer/AttachmentNormalizer.php
index 7911a9c3..c71e035d 100644
--- a/src/Serializer/AttachmentNormalizer.php
+++ b/src/Serializer/AttachmentNormalizer.php
@@ -40,7 +40,7 @@ class AttachmentNormalizer implements NormalizerInterface
 
     }
 
-    public function normalize(mixed $object, string $format = null, array $context = [])
+    public function normalize(mixed $object, string $format = null, array $context = []): array|null
     {
         if (!$object instanceof Attachment) {
             throw new \InvalidArgumentException('This normalizer only supports Attachment objects!');
diff --git a/src/Serializer/BigNumberNormalizer.php b/src/Serializer/BigNumberNormalizer.php
index 80bb98d7..8ef06d67 100644
--- a/src/Serializer/BigNumberNormalizer.php
+++ b/src/Serializer/BigNumberNormalizer.php
@@ -58,7 +58,7 @@ class BigNumberNormalizer implements NormalizerInterface, DenormalizerInterface
         ];
     }
 
-    public function denormalize(mixed $data, string $type, string $format = null, array $context = [])
+    public function denormalize(mixed $data, string $type, string $format = null, array $context = []): BigNumber|null
     {
         if (!is_a($type, BigNumber::class, true)) {
             throw new \InvalidArgumentException('This normalizer only supports BigNumber objects!');
@@ -67,7 +67,7 @@ class BigNumberNormalizer implements NormalizerInterface, DenormalizerInterface
         return $type::of($data);
     }
 
-    public function supportsDenormalization(mixed $data, string $type, string $format = null)
+    public function supportsDenormalization(mixed $data, string $type, string $format = null, array $context = []): bool
     {
         //data must be a string or a number (int, float, etc.) and the type must be BigNumber or BigDecimal
         return (is_string($data) || is_numeric($data)) && (is_subclass_of($type, BigNumber::class));
diff --git a/src/Services/SnakeCasePropertyAccessExtractor.php b/src/Services/SnakeCasePropertyAccessExtractor.php
index bfe82c63..0eaed204 100644
--- a/src/Services/SnakeCasePropertyAccessExtractor.php
+++ b/src/Services/SnakeCasePropertyAccessExtractor.php
@@ -41,7 +41,7 @@ class SnakeCasePropertyAccessExtractor implements PropertyAccessExtractorInterfa
         //$this->reflectionExtractor = new ReflectionExtractor();
     }
 
-    public function isReadable(string $class, string $property, array $context = [])
+    public function isReadable(string $class, string $property, array $context = []): ?bool
     {
         //Null means skip this extractor
         return null;
@@ -56,7 +56,7 @@ class SnakeCasePropertyAccessExtractor implements PropertyAccessExtractorInterfa
     }
 
 
-    public function isWritable(string $class, string $property, array $context = [])
+    public function isWritable(string $class, string $property, array $context = []): ?bool
     {
         //Check writeablity using a camelized property name
         $isWriteable = $this->reflectionExtractor->isWritable($class, $this->camelize($property), $context);
diff --git a/src/Validator/Constraints/UniqueObjectCollectionValidator.php b/src/Validator/Constraints/UniqueObjectCollectionValidator.php
index 5522ca19..eaac097d 100644
--- a/src/Validator/Constraints/UniqueObjectCollectionValidator.php
+++ b/src/Validator/Constraints/UniqueObjectCollectionValidator.php
@@ -32,7 +32,7 @@ use Symfony\Component\Validator\Exception\UnexpectedValueException;
 class UniqueObjectCollectionValidator extends ConstraintValidator
 {
 
-    public function validate(mixed $value, Constraint $constraint)
+    public function validate(mixed $value, Constraint $constraint): void
     {
         if (!$constraint instanceof UniqueObjectCollection) {
             throw new UnexpectedTypeException($constraint, UniqueObjectCollection::class);
diff --git a/tests/Validator/Constraints/ValidGoogleAuthCodeValidatorTest.php b/tests/Validator/Constraints/ValidGoogleAuthCodeValidatorTest.php
index 6b3887e4..5ba98a47 100644
--- a/tests/Validator/Constraints/ValidGoogleAuthCodeValidatorTest.php
+++ b/tests/Validator/Constraints/ValidGoogleAuthCodeValidatorTest.php
@@ -28,22 +28,21 @@ use Scheb\TwoFactorBundle\Model\Google\TwoFactorInterface;
 use Scheb\TwoFactorBundle\Security\TwoFactor\Provider\Google\GoogleAuthenticatorInterface;
 use Symfony\Bundle\SecurityBundle\Security;
 use Symfony\Component\Security\Core\User\UserInterface;
+use Symfony\Component\Validator\ConstraintValidator;
+use Symfony\Component\Validator\ConstraintValidatorInterface;
 use Symfony\Component\Validator\Test\ConstraintValidatorTestCase;
 
 class ValidGoogleAuthCodeValidatorTest extends ConstraintValidatorTestCase
 {
 
-    protected function createValidator()
+    protected function createValidator(): ConstraintValidatorInterface
     {
         $googleAuth = new class implements GoogleAuthenticatorInterface
         {
 
             public function checkCode(TwoFactorInterface $user, string $code): bool
             {
-                if ($code === '123456') {
-                    return true;
-                }
-                return false;
+                return $code === '123456';
             }
 
             public function getQRContent(TwoFactorInterface $user): string