diff --git a/config/test/bootstrap_api_tests.php b/config/test/bootstrap_api_tests.php
index 3605427c..4cf01807 100644
--- a/config/test/bootstrap_api_tests.php
+++ b/config/test/bootstrap_api_tests.php
@@ -15,6 +15,4 @@ $em = $container->get(EntityManager::class);
 
 $testHelper->createTestDb();
 ApiTest\ApiTestCase::setApiClient($container->get('shlink_test_api_client'));
-ApiTest\ApiTestCase::setSeedFixturesCallback(function () use ($testHelper, $em, $config) {
-    $testHelper->seedFixtures($em, $config['data_fixtures'] ?? []);
-});
+ApiTest\ApiTestCase::setSeedFixturesCallback(fn () => $testHelper->seedFixtures($em, $config['data_fixtures'] ?? []));
diff --git a/config/test/test_config.global.php b/config/test/test_config.global.php
index a0a9aeb7..0aeaea6d 100644
--- a/config/test/test_config.global.php
+++ b/config/test/test_config.global.php
@@ -19,9 +19,7 @@ $swooleTestingPort = 9999;
 $buildDbConnection = function (): array {
     $driver = env('DB_DRIVER', 'sqlite');
     $isCi = env('TRAVIS', false);
-    $getMysqlHost = function (string $driver) {
-        return sprintf('shlink_db%s', $driver === 'mysql' ? '' : '_maria');
-    };
+    $getMysqlHost = fn (string $driver) => sprintf('shlink_db%s', $driver === 'mysql' ? '' : '_maria');
 
     $driverConfigMap = [
         'sqlite' => [
diff --git a/module/CLI/src/Command/Tag/ListTagsCommand.php b/module/CLI/src/Command/Tag/ListTagsCommand.php
index e4059291..0b8f0aa3 100644
--- a/module/CLI/src/Command/Tag/ListTagsCommand.php
+++ b/module/CLI/src/Command/Tag/ListTagsCommand.php
@@ -46,8 +46,6 @@ class ListTagsCommand extends Command
             return [['No tags yet']];
         }
 
-        return map($tags, function (Tag $tag) {
-            return [(string) $tag];
-        });
+        return map($tags, fn (Tag $tag) => [(string) $tag]);
     }
 }
diff --git a/module/CLI/test/Command/ShortUrl/ListShortUrlsCommandTest.php b/module/CLI/test/Command/ShortUrl/ListShortUrlsCommandTest.php
index 5fc3ecee..a704111d 100644
--- a/module/CLI/test/Command/ShortUrl/ListShortUrlsCommandTest.php
+++ b/module/CLI/test/Command/ShortUrl/ListShortUrlsCommandTest.php
@@ -42,9 +42,9 @@ class ListShortUrlsCommandTest extends TestCase
             $data[] = new ShortUrl('url_' . $i);
         }
 
-        $this->shortUrlService->listShortUrls(Argument::cetera())->will(function () use (&$data) {
-            return new Paginator(new ArrayAdapter($data));
-        })->shouldBeCalledTimes(3);
+        $this->shortUrlService->listShortUrls(Argument::cetera())
+            ->will(fn () => new Paginator(new ArrayAdapter($data)))
+            ->shouldBeCalledTimes(3);
 
         $this->commandTester->setInputs(['y', 'y', 'n']);
         $this->commandTester->execute([]);
diff --git a/module/CLI/test/Util/GeolocationDbUpdaterTest.php b/module/CLI/test/Util/GeolocationDbUpdaterTest.php
index 7120c735..640c0e7c 100644
--- a/module/CLI/test/Util/GeolocationDbUpdaterTest.php
+++ b/module/CLI/test/Util/GeolocationDbUpdaterTest.php
@@ -50,9 +50,7 @@ class GeolocationDbUpdaterTest extends TestCase
     /** @test */
     public function exceptionIsThrownWhenOlderDbDoesNotExistAndDownloadFails(): void
     {
-        $mustBeUpdated = function () {
-            $this->assertTrue(true);
-        };
+        $mustBeUpdated = fn () => $this->assertTrue(true);
         $prev = new RuntimeException('');
 
         $fileExists = $this->dbUpdater->databaseFileExists()->willReturn(false);
@@ -148,8 +146,6 @@ class GeolocationDbUpdaterTest extends TestCase
 
     public function provideSmallDays(): iterable
     {
-        return map(range(0, 34), function (int $days) {
-            return [$days];
-        });
+        return map(range(0, 34), fn (int $days) => [$days]);
     }
 }
diff --git a/module/Core/src/Config/SimplifiedConfigParser.php b/module/Core/src/Config/SimplifiedConfigParser.php
index 5ee912b0..e9c2ae7b 100644
--- a/module/Core/src/Config/SimplifiedConfigParser.php
+++ b/module/Core/src/Config/SimplifiedConfigParser.php
@@ -75,9 +75,10 @@ class SimplifiedConfigParser
         // This mainly allows deprecating keys and defining new ones that will replace the older and always take
         // preference, while the old one keeps working for backwards compatibility if the new one is not provided.
         $simplifiedConfigOrder = array_flip(array_keys(self::SIMPLIFIED_CONFIG_MAPPING));
-        uksort($configForExistingKeys, function (string $a, string $b) use ($simplifiedConfigOrder): int {
-            return $simplifiedConfigOrder[$a] - $simplifiedConfigOrder[$b];
-        });
+        uksort(
+            $configForExistingKeys,
+            fn (string $a, string $b): int => $simplifiedConfigOrder[$a] - $simplifiedConfigOrder[$b]
+        );
 
         return $configForExistingKeys;
     }
diff --git a/module/Core/src/Entity/ShortUrl.php b/module/Core/src/Entity/ShortUrl.php
index ef8a3b2f..64d6d4b5 100644
--- a/module/Core/src/Entity/ShortUrl.php
+++ b/module/Core/src/Entity/ShortUrl.php
@@ -188,9 +188,7 @@ class ShortUrl extends AbstractEntity
         $shortUrlTags = invoke($this->getTags(), '__toString');
         $hasAllTags = count($shortUrlTags) === count($tags) && array_reduce(
             $tags,
-            function (bool $hasAllTags, string $tag) use ($shortUrlTags) {
-                return $hasAllTags && contains($shortUrlTags, $tag);
-            },
+            fn (bool $hasAllTags, string $tag) => $hasAllTags && contains($shortUrlTags, $tag),
             true
         );
 
diff --git a/module/Core/src/Exception/ValidationException.php b/module/Core/src/Exception/ValidationException.php
index c2308f06..8710b737 100644
--- a/module/Core/src/Exception/ValidationException.php
+++ b/module/Core/src/Exception/ValidationException.php
@@ -69,12 +69,10 @@ class ValidationException extends InvalidArgumentException implements ProblemDet
 
     private function invalidElementsToString(): string
     {
-        return reduce_left($this->getInvalidElements(), function ($messageSet, string $name, $_, string $acc) {
-            return $acc . sprintf(
-                "\n    '%s' => %s",
-                $name,
-                is_array($messageSet) ? print_r($messageSet, true) : $messageSet
-            );
-        }, '');
+        return reduce_left($this->getInvalidElements(), fn ($messages, string $name, $_, string $acc) => $acc . sprintf(
+            "\n    '%s' => %s",
+            $name,
+            is_array($messages) ? print_r($messages, true) : $messages
+        ), '');
     }
 }
diff --git a/module/Core/test-db/Repository/VisitRepositoryTest.php b/module/Core/test-db/Repository/VisitRepositoryTest.php
index 51ffbc3c..bbccea41 100644
--- a/module/Core/test-db/Repository/VisitRepositoryTest.php
+++ b/module/Core/test-db/Repository/VisitRepositoryTest.php
@@ -66,9 +66,7 @@ class VisitRepositoryTest extends DatabaseTestCase
 
     public function provideBlockSize(): iterable
     {
-        return map(range(1, 5), function (int $value) {
-            return [$value];
-        });
+        return map(range(1, 5), fn (int $value) => [$value]);
     }
 
     /** @test */
diff --git a/module/Core/test/Service/ShortUrl/DeleteShortUrlServiceTest.php b/module/Core/test/Service/ShortUrl/DeleteShortUrlServiceTest.php
index 22dddcb5..b708e465 100644
--- a/module/Core/test/Service/ShortUrl/DeleteShortUrlServiceTest.php
+++ b/module/Core/test/Service/ShortUrl/DeleteShortUrlServiceTest.php
@@ -28,9 +28,9 @@ class DeleteShortUrlServiceTest extends TestCase
 
     public function setUp(): void
     {
-        $shortUrl = (new ShortUrl(''))->setVisits(new ArrayCollection(map(range(0, 10), function () {
-            return new Visit(new ShortUrl(''), Visitor::emptyInstance());
-        })));
+        $shortUrl = (new ShortUrl(''))->setVisits(
+            new ArrayCollection(map(range(0, 10), fn () => new Visit(new ShortUrl(''), Visitor::emptyInstance())))
+        );
         $this->shortCode = $shortUrl->getShortCode();
 
         $this->em = $this->prophesize(EntityManagerInterface::class);
diff --git a/module/Core/test/Service/UrlShortenerTest.php b/module/Core/test/Service/UrlShortenerTest.php
index 25720671..9d183381 100644
--- a/module/Core/test/Service/UrlShortenerTest.php
+++ b/module/Core/test/Service/UrlShortenerTest.php
@@ -44,7 +44,7 @@ class UrlShortenerTest extends TestCase
         $this->em->beginTransaction()->willReturn(null);
         $this->em->persist(Argument::any())->will(function ($arguments) {
             /** @var ShortUrl $shortUrl */
-            $shortUrl = $arguments[0];
+            [$shortUrl] = $arguments;
             $shortUrl->setId('10');
         });
         $repo = $this->prophesize(ShortUrlRepository::class);
@@ -240,9 +240,7 @@ class UrlShortenerTest extends TestCase
             'validUntil' => Chronos::parse('2017-01-01'),
             'maxVisits' => 4,
         ]);
-        $tagsCollection = new ArrayCollection(array_map(function (string $tag) {
-            return new Tag($tag);
-        }, $tags));
+        $tagsCollection = new ArrayCollection(array_map(fn (string $tag) => new Tag($tag), $tags));
         $expected = (new ShortUrl($url, $meta))->setTags($tagsCollection);
 
         $repo = $this->prophesize(ShortUrlRepository::class);
diff --git a/module/Core/test/Service/VisitServiceTest.php b/module/Core/test/Service/VisitServiceTest.php
index 42b201b2..e09b0a4c 100644
--- a/module/Core/test/Service/VisitServiceTest.php
+++ b/module/Core/test/Service/VisitServiceTest.php
@@ -40,9 +40,10 @@ class VisitServiceTest extends TestCase
     /** @test */
     public function locateVisitsIteratesAndLocatesUnlocatedVisits(): void
     {
-        $unlocatedVisits = map(range(1, 200), function (int $i) {
-            return new Visit(new ShortUrl(sprintf('short_code_%s', $i)), Visitor::emptyInstance());
-        });
+        $unlocatedVisits = map(
+            range(1, 200),
+            fn (int $i) => new Visit(new ShortUrl(sprintf('short_code_%s', $i)), Visitor::emptyInstance())
+        );
 
         $repo = $this->prophesize(VisitRepository::class);
         $findUnlocatedVisits = $repo->findUnlocatedVisits(false)->willReturn($unlocatedVisits);
@@ -55,9 +56,7 @@ class VisitServiceTest extends TestCase
         $clear = $this->em->clear()->will(function () {
         });
 
-        $this->visitService->locateUnlocatedVisits(function () {
-            return Location::emptyInstance();
-        }, function () {
+        $this->visitService->locateUnlocatedVisits(fn () => Location::emptyInstance(), function () {
             $args = func_get_args();
 
             $this->assertInstanceOf(VisitLocation::class, array_shift($args));
diff --git a/module/Core/test/Service/VisitsTrackerTest.php b/module/Core/test/Service/VisitsTrackerTest.php
index 0cb4d205..9b9ab948 100644
--- a/module/Core/test/Service/VisitsTrackerTest.php
+++ b/module/Core/test/Service/VisitsTrackerTest.php
@@ -43,10 +43,7 @@ class VisitsTrackerTest extends TestCase
         $repo->findOneBy(['shortCode' => $shortCode])->willReturn(new ShortUrl(''));
 
         $this->em->getRepository(ShortUrl::class)->willReturn($repo->reveal())->shouldBeCalledOnce();
-        $this->em->persist(Argument::that(function (Visit $visit) {
-            $visit->setId('1');
-            return $visit;
-        }))->shouldBeCalledOnce();
+        $this->em->persist(Argument::that(fn (Visit $visit) => $visit->setId('1')))->shouldBeCalledOnce();
         $this->em->flush()->shouldBeCalledOnce();
 
         $this->visitsTracker->track($shortCode, Visitor::emptyInstance());
diff --git a/module/Rest/src/Authentication/RequestToHttpAuthPlugin.php b/module/Rest/src/Authentication/RequestToHttpAuthPlugin.php
index 9496ceff..bb6454b2 100644
--- a/module/Rest/src/Authentication/RequestToHttpAuthPlugin.php
+++ b/module/Rest/src/Authentication/RequestToHttpAuthPlugin.php
@@ -43,9 +43,7 @@ class RequestToHttpAuthPlugin implements RequestToHttpAuthPluginInterface
     {
         return array_reduce(
             self::SUPPORTED_AUTH_HEADERS,
-            function (bool $carry, string $header) use ($request) {
-                return $carry || $request->hasHeader($header);
-            },
+            fn (bool $carry, string $header) => $carry || $request->hasHeader($header),
             false
         );
     }
diff --git a/module/Rest/src/Middleware/EmptyResponseImplicitOptionsMiddlewareFactory.php b/module/Rest/src/Middleware/EmptyResponseImplicitOptionsMiddlewareFactory.php
index 06cdc435..5075e244 100644
--- a/module/Rest/src/Middleware/EmptyResponseImplicitOptionsMiddlewareFactory.php
+++ b/module/Rest/src/Middleware/EmptyResponseImplicitOptionsMiddlewareFactory.php
@@ -11,8 +11,6 @@ class EmptyResponseImplicitOptionsMiddlewareFactory
 {
     public function __invoke()
     {
-        return new ImplicitOptionsMiddleware(function () {
-            return new EmptyResponse();
-        });
+        return new ImplicitOptionsMiddleware(fn () => new EmptyResponse());
     }
 }
diff --git a/module/Rest/test-api/Action/CreateShortUrlActionTest.php b/module/Rest/test-api/Action/CreateShortUrlActionTest.php
index 37a2630c..efff5f33 100644
--- a/module/Rest/test-api/Action/CreateShortUrlActionTest.php
+++ b/module/Rest/test-api/Action/CreateShortUrlActionTest.php
@@ -91,9 +91,7 @@ class CreateShortUrlActionTest extends ApiTestCase
 
     public function provideMaxVisits(): array
     {
-        return map(range(10, 15), function (int $i) {
-            return [$i];
-        });
+        return map(range(10, 15), fn (int $i) => [$i]);
     }
 
     /** @test */
diff --git a/module/Rest/test/Authentication/AuthenticationPluginManagerFactoryTest.php b/module/Rest/test/Authentication/AuthenticationPluginManagerFactoryTest.php
index 71bcfe9c..4c24e26a 100644
--- a/module/Rest/test/Authentication/AuthenticationPluginManagerFactoryTest.php
+++ b/module/Rest/test/Authentication/AuthenticationPluginManagerFactoryTest.php
@@ -34,9 +34,7 @@ class AuthenticationPluginManagerFactoryTest extends TestCase
 
     private function getPlugins(AuthenticationPluginManager $pluginManager): array
     {
-        return (function () {
-            return $this->services;
-        })->call($pluginManager);
+        return (fn () => $this->services)->call($pluginManager);
     }
 
     public function provideConfigs(): iterable
diff --git a/module/Rest/test/ConfigProviderTest.php b/module/Rest/test/ConfigProviderTest.php
index f914edf6..b8cebf93 100644
--- a/module/Rest/test/ConfigProviderTest.php
+++ b/module/Rest/test/ConfigProviderTest.php
@@ -28,15 +28,13 @@ class ConfigProviderTest extends TestCase
     /** @test */
     public function routesAreProperlyPrefixed(): void
     {
-        $configProvider = new ConfigProvider(function () {
-            return [
-                'routes' => [
-                    ['path' => '/foo'],
-                    ['path' => '/bar'],
-                    ['path' => '/baz/foo'],
-                ],
-            ];
-        });
+        $configProvider = new ConfigProvider(fn () => [
+            'routes' => [
+                ['path' => '/foo'],
+                ['path' => '/bar'],
+                ['path' => '/baz/foo'],
+            ],
+        ]);
 
         $config = $configProvider();
 
diff --git a/module/Rest/test/Middleware/AuthenticationMiddlewareTest.php b/module/Rest/test/Middleware/AuthenticationMiddlewareTest.php
index 8f9e8052..8bef98a1 100644
--- a/module/Rest/test/Middleware/AuthenticationMiddlewareTest.php
+++ b/module/Rest/test/Middleware/AuthenticationMiddlewareTest.php
@@ -109,8 +109,6 @@ class AuthenticationMiddlewareTest extends TestCase
 
     private function getDummyMiddleware(): MiddlewareInterface
     {
-        return middleware(function () {
-            return new Response\EmptyResponse();
-        });
+        return middleware(fn () => new Response\EmptyResponse());
     }
 }