diff --git a/src/Symfony/Bridge/Doctrine/Tests/Form/Type/EntityTypeTest.php b/src/Symfony/Bridge/Doctrine/Tests/Form/Type/EntityTypeTest.php
index ec8f7933f9..fa03960ad4 100644
--- a/src/Symfony/Bridge/Doctrine/Tests/Form/Type/EntityTypeTest.php
+++ b/src/Symfony/Bridge/Doctrine/Tests/Form/Type/EntityTypeTest.php
@@ -60,6 +60,13 @@ class EntityTypeTest extends BaseTypeTest
 
     protected static $supportedFeatureSetVersion = 404;
 
+    public static function setUpBeforeClass(): void
+    {
+        if (\PHP_VERSION_ID >= 80000) {
+            self::markTestSkipped('Doctrine DBAL 2.x is incompatible with PHP 8.');
+        }
+    }
+
     protected function setUp(): void
     {
         $this->em = DoctrineTestHelper::createTestEntityManager();
diff --git a/src/Symfony/Bridge/Doctrine/Tests/Security/User/EntityUserProviderTest.php b/src/Symfony/Bridge/Doctrine/Tests/Security/User/EntityUserProviderTest.php
index 10ff2ff259..cb809abbaf 100644
--- a/src/Symfony/Bridge/Doctrine/Tests/Security/User/EntityUserProviderTest.php
+++ b/src/Symfony/Bridge/Doctrine/Tests/Security/User/EntityUserProviderTest.php
@@ -24,6 +24,13 @@ use Symfony\Component\Security\Core\User\PasswordUpgraderInterface;
 
 class EntityUserProviderTest extends TestCase
 {
+    public static function setUpBeforeClass(): void
+    {
+        if (\PHP_VERSION_ID >= 80000) {
+            self::markTestSkipped('Doctrine DBAL 2.x is incompatible with PHP 8.');
+        }
+    }
+
     public function testRefreshUserGetsUserByPrimaryKey()
     {
         $em = DoctrineTestHelper::createTestEntityManager();
diff --git a/src/Symfony/Bridge/Doctrine/Tests/Validator/Constraints/UniqueEntityValidatorTest.php b/src/Symfony/Bridge/Doctrine/Tests/Validator/Constraints/UniqueEntityValidatorTest.php
index e9e905c89c..985d4601bf 100644
--- a/src/Symfony/Bridge/Doctrine/Tests/Validator/Constraints/UniqueEntityValidatorTest.php
+++ b/src/Symfony/Bridge/Doctrine/Tests/Validator/Constraints/UniqueEntityValidatorTest.php
@@ -59,6 +59,13 @@ class UniqueEntityValidatorTest extends ConstraintValidatorTestCase
 
     protected $repositoryFactory;
 
+    public static function setUpBeforeClass(): void
+    {
+        if (\PHP_VERSION_ID >= 80000) {
+            self::markTestSkipped('Doctrine DBAL 2.x is incompatible with PHP 8.');
+        }
+    }
+
     protected function setUp(): void
     {
         $this->repositoryFactory = new TestRepositoryFactory();
diff --git a/src/Symfony/Component/Cache/composer.json b/src/Symfony/Component/Cache/composer.json
index 6d8754ac5e..e24f6f1912 100644
--- a/src/Symfony/Component/Cache/composer.json
+++ b/src/Symfony/Component/Cache/composer.json
@@ -30,9 +30,9 @@
     },
     "require-dev": {
         "cache/integration-tests": "dev-master",
-        "doctrine/cache": "~1.6",
-        "doctrine/dbal": "~2.5",
-        "predis/predis": "~1.1",
+        "doctrine/cache": "^1.6",
+        "doctrine/dbal": "^2.5|^3.0",
+        "predis/predis": "^1.1",
         "psr/simple-cache": "^1.0",
         "symfony/config": "^4.2|^5.0",
         "symfony/dependency-injection": "^3.4|^4.1|^5.0",
diff --git a/src/Symfony/Component/Config/Resource/ReflectionClassResource.php b/src/Symfony/Component/Config/Resource/ReflectionClassResource.php
index 48fdcd69b0..f386e4524f 100644
--- a/src/Symfony/Component/Config/Resource/ReflectionClassResource.php
+++ b/src/Symfony/Component/Config/Resource/ReflectionClassResource.php
@@ -135,7 +135,11 @@ class ReflectionClassResource implements SelfCheckingResourceInterface
             $defaults = $class->getDefaultProperties();
 
             foreach ($class->getProperties(\ReflectionProperty::IS_PUBLIC | \ReflectionProperty::IS_PROTECTED) as $p) {
-                yield $p->getDocComment().$p;
+                yield $p->getDocComment();
+                yield $p->isDefault() ? '<default>' : '';
+                yield $p->isPublic() ? 'public' : 'protected';
+                yield $p->isStatic() ? 'static' : '';
+                yield '$'.$p->name;
                 yield print_r(isset($defaults[$p->name]) && !\is_object($defaults[$p->name]) ? $defaults[$p->name] : null, true);
             }
         }
diff --git a/src/Symfony/Component/Debug/Tests/ErrorHandlerTest.php b/src/Symfony/Component/Debug/Tests/ErrorHandlerTest.php
index fcead4f84e..2ba84c171b 100644
--- a/src/Symfony/Component/Debug/Tests/ErrorHandlerTest.php
+++ b/src/Symfony/Component/Debug/Tests/ErrorHandlerTest.php
@@ -103,9 +103,14 @@ class ErrorHandlerTest extends TestCase
             $this->fail('ErrorException expected');
         } catch (\ErrorException $exception) {
             // if an exception is thrown, the test passed
-            $this->assertEquals(E_NOTICE, $exception->getSeverity());
+            if (\PHP_VERSION_ID < 80000) {
+                $this->assertEquals(E_NOTICE, $exception->getSeverity());
+                $this->assertRegExp('/^Notice: Undefined variable: (foo|bar)/', $exception->getMessage());
+            } else {
+                $this->assertEquals(E_WARNING, $exception->getSeverity());
+                $this->assertRegExp('/^Warning: Undefined variable \$(foo|bar)/', $exception->getMessage());
+            }
             $this->assertEquals(__FILE__, $exception->getFile());
-            $this->assertRegExp('/^Notice: Undefined variable: (foo|bar)/', $exception->getMessage());
 
             $trace = $exception->getTrace();
 
@@ -249,11 +254,17 @@ class ErrorHandlerTest extends TestCase
 
             $line = null;
             $logArgCheck = function ($level, $message, $context) use (&$line) {
-                $this->assertEquals('Notice: Undefined variable: undefVar', $message);
                 $this->assertArrayHasKey('exception', $context);
                 $exception = $context['exception'];
+
+                if (\PHP_VERSION_ID < 80000) {
+                    $this->assertEquals('Notice: Undefined variable: undefVar', $message);
+                    $this->assertSame(E_NOTICE, $exception->getSeverity());
+                } else {
+                    $this->assertEquals('Warning: Undefined variable $undefVar', $message);
+                    $this->assertSame(E_WARNING, $exception->getSeverity());
+                }
                 $this->assertInstanceOf(SilencedErrorContext::class, $exception);
-                $this->assertSame(E_NOTICE, $exception->getSeverity());
                 $this->assertSame(__FILE__, $exception->getFile());
                 $this->assertSame($line, $exception->getLine());
                 $this->assertNotEmpty($exception->getTrace());
@@ -267,8 +278,13 @@ class ErrorHandlerTest extends TestCase
             ;
 
             $handler = ErrorHandler::register();
-            $handler->setDefaultLogger($logger, E_NOTICE);
-            $handler->screamAt(E_NOTICE);
+            if (\PHP_VERSION_ID < 80000) {
+                $handler->setDefaultLogger($logger, E_NOTICE);
+                $handler->screamAt(E_NOTICE);
+            } else {
+                $handler->setDefaultLogger($logger, E_WARNING);
+                $handler->screamAt(E_WARNING);
+            }
             unset($undefVar);
             $line = __LINE__ + 1;
             @$undefVar++;
diff --git a/src/Symfony/Component/Debug/Tests/Fixtures/ErrorHandlerThatUsesThePreviousOne.php b/src/Symfony/Component/Debug/Tests/Fixtures/ErrorHandlerThatUsesThePreviousOne.php
index d449c40cc7..bb2fba51f0 100644
--- a/src/Symfony/Component/Debug/Tests/Fixtures/ErrorHandlerThatUsesThePreviousOne.php
+++ b/src/Symfony/Component/Debug/Tests/Fixtures/ErrorHandlerThatUsesThePreviousOne.php
@@ -15,8 +15,8 @@ class ErrorHandlerThatUsesThePreviousOne
         return $handler;
     }
 
-    public function handleError($type, $message, $file, $line, $context)
+    public function handleError()
     {
-        return \call_user_func(self::$previous, $type, $message, $file, $line, $context);
+        return \call_user_func_array(self::$previous, \func_get_args());
     }
 }
diff --git a/src/Symfony/Component/HttpFoundation/File/UploadedFile.php b/src/Symfony/Component/HttpFoundation/File/UploadedFile.php
index 36fd1e65cf..5d5063e46b 100644
--- a/src/Symfony/Component/HttpFoundation/File/UploadedFile.php
+++ b/src/Symfony/Component/HttpFoundation/File/UploadedFile.php
@@ -31,7 +31,7 @@ use Symfony\Component\Mime\MimeTypes;
  */
 class UploadedFile extends File
 {
-    private $test = false;
+    private $test;
     private $originalName;
     private $mimeType;
     private $error;
@@ -83,7 +83,7 @@ class UploadedFile extends File
      * It is extracted from the request from which the file has been uploaded.
      * Then it should not be considered as a safe value.
      *
-     * @return string|null The original name
+     * @return string The original name
      */
     public function getClientOriginalName()
     {
@@ -112,7 +112,7 @@ class UploadedFile extends File
      * For a trusted mime type, use getMimeType() instead (which guesses the mime
      * type based on the file content).
      *
-     * @return string|null The mime type
+     * @return string The mime type
      *
      * @see getMimeType()
      */
diff --git a/src/Symfony/Component/Intl/Tests/NumberFormatter/AbstractNumberFormatterTest.php b/src/Symfony/Component/Intl/Tests/NumberFormatter/AbstractNumberFormatterTest.php
index 9802a66b9a..ba94ce041e 100644
--- a/src/Symfony/Component/Intl/Tests/NumberFormatter/AbstractNumberFormatterTest.php
+++ b/src/Symfony/Component/Intl/Tests/NumberFormatter/AbstractNumberFormatterTest.php
@@ -602,7 +602,7 @@ abstract class AbstractNumberFormatterTest extends TestCase
 
         $r = new \ReflectionProperty('Symfony\Component\Intl\NumberFormatter\NumberFormatter', 'enSymbols');
         $r->setAccessible(true);
-        $expected = $r->getValue('Symfony\Component\Intl\NumberFormatter\NumberFormatter');
+        $expected = $r->getValue();
 
         for ($i = 0; $i <= 17; ++$i) {
             $this->assertSame($expected[1][$i], $decimalFormatter->getSymbol($i));
@@ -619,7 +619,7 @@ abstract class AbstractNumberFormatterTest extends TestCase
 
         $r = new \ReflectionProperty('Symfony\Component\Intl\NumberFormatter\NumberFormatter', 'enTextAttributes');
         $r->setAccessible(true);
-        $expected = $r->getValue('Symfony\Component\Intl\NumberFormatter\NumberFormatter');
+        $expected = $r->getValue();
 
         for ($i = 0; $i <= 5; ++$i) {
             $this->assertSame($expected[1][$i], $decimalFormatter->getTextAttribute($i));
diff --git a/src/Symfony/Component/OptionsResolver/OptionsResolver.php b/src/Symfony/Component/OptionsResolver/OptionsResolver.php
index c9c092a6bb..bc2546397a 100644
--- a/src/Symfony/Component/OptionsResolver/OptionsResolver.php
+++ b/src/Symfony/Component/OptionsResolver/OptionsResolver.php
@@ -180,7 +180,7 @@ class OptionsResolver implements Options
             $reflClosure = new \ReflectionFunction($value);
             $params = $reflClosure->getParameters();
 
-            if (isset($params[0]) && null !== ($class = $params[0]->getClass()) && Options::class === $class->name) {
+            if (isset($params[0]) && Options::class === $this->getParameterClassName($params[0])) {
                 // Initialize the option if no previous value exists
                 if (!isset($this->defaults[$option])) {
                     $this->defaults[$option] = null;
@@ -1217,4 +1217,13 @@ class OptionsResolver implements Options
 
         return implode('", "', $options);
     }
+
+    private function getParameterClassName(\ReflectionParameter $parameter): ?string
+    {
+        if (!($type = $parameter->getType()) || $type->isBuiltin()) {
+            return null;
+        }
+
+        return $type->getName();
+    }
 }
diff --git a/src/Symfony/Component/PropertyAccess/PropertyAccessor.php b/src/Symfony/Component/PropertyAccess/PropertyAccessor.php
index cac049a0a6..2d47e3d256 100644
--- a/src/Symfony/Component/PropertyAccess/PropertyAccessor.php
+++ b/src/Symfony/Component/PropertyAccess/PropertyAccessor.php
@@ -183,12 +183,15 @@ class PropertyAccessor implements PropertyAccessorInterface
 
     private static function throwInvalidArgumentException(string $message, array $trace, int $i, string $propertyPath, \Throwable $previous = null): void
     {
-        // the type mismatch is not caused by invalid arguments (but e.g. by an incompatible return type hint of the writer method)
-        if (0 !== strpos($message, 'Argument ')) {
+        if (!isset($trace[$i]['file']) || __FILE__ !== $trace[$i]['file']) {
             return;
         }
 
-        if (isset($trace[$i]['file']) && __FILE__ === $trace[$i]['file']) {
+        if (\PHP_VERSION_ID < 80000) {
+            if (0 !== strpos($message, 'Argument ')) {
+                return;
+            }
+
             $pos = strpos($message, $delim = 'must be of the type ') ?: (strpos($message, $delim = 'must be an instance of ') ?: strpos($message, $delim = 'must implement interface '));
             $pos += \strlen($delim);
             $j = strpos($message, ',', $pos);
@@ -197,6 +200,12 @@ class PropertyAccessor implements PropertyAccessorInterface
 
             throw new InvalidArgumentException(sprintf('Expected argument of type "%s", "%s" given at property path "%s".', $message, 'NULL' === $type ? 'null' : $type, $propertyPath), 0, $previous);
         }
+
+        if (preg_match('/^\S+::\S+\(\): Argument #\d+ \(\$\S+\) must be of type (\S+), (\S+) given/', $message, $matches)) {
+            list(, $expectedType, $actualType) = $matches;
+
+            throw new InvalidArgumentException(sprintf('Expected argument of type "%s", "%s" given.', $expectedType, 'NULL' === $actualType ? 'null' : $actualType), 0, $previous);
+        }
     }
 
     /**
@@ -384,7 +393,7 @@ class PropertyAccessor implements PropertyAccessorInterface
                     $result[self::VALUE] = $object->{$access[self::ACCESS_NAME]}();
                 } catch (\TypeError $e) {
                     // handle uninitialized properties in PHP >= 7
-                    if (preg_match((sprintf('/^Return value of %s::%s\(\) must be of the type (\w+), null returned$/', preg_quote(\get_class($object)), $access[self::ACCESS_NAME])), $e->getMessage(), $matches)) {
+                    if (preg_match((sprintf('/^Return value of %s::%s\(\) must be of (?:the )?type (\w+), null returned$/', preg_quote(\get_class($object)), $access[self::ACCESS_NAME])), $e->getMessage(), $matches)) {
                         throw new AccessException(sprintf('The method "%s::%s()" returned "null", but expected type "%3$s". Did you forget to initialize a property or to make the return type nullable using "?%3$s"?', \get_class($object), $access[self::ACCESS_NAME], $matches[1]), 0, $e);
                     }
 
diff --git a/src/Symfony/Component/Validator/Constraints/LengthValidator.php b/src/Symfony/Component/Validator/Constraints/LengthValidator.php
index f49c681bf8..104895d120 100644
--- a/src/Symfony/Component/Validator/Constraints/LengthValidator.php
+++ b/src/Symfony/Component/Validator/Constraints/LengthValidator.php
@@ -48,8 +48,14 @@ class LengthValidator extends ConstraintValidator
             $stringValue = ($constraint->normalizer)($stringValue);
         }
 
-        if (!$invalidCharset = !@mb_check_encoding($stringValue, $constraint->charset)) {
-            $length = mb_strlen($stringValue, $constraint->charset);
+        try {
+            $invalidCharset = !@mb_check_encoding($stringValue, $constraint->charset);
+        } catch (\ValueError $e) {
+            if (!str_starts_with($e->getMessage(), 'mb_check_encoding(): Argument #2 ($encoding) must be a valid encoding')) {
+                throw $e;
+            }
+
+            $invalidCharset = true;
         }
 
         if ($invalidCharset) {
@@ -63,6 +69,8 @@ class LengthValidator extends ConstraintValidator
             return;
         }
 
+        $length = mb_strlen($stringValue, $constraint->charset);
+
         if (null !== $constraint->max && $length > $constraint->max) {
             $this->context->buildViolation($constraint->min == $constraint->max ? $constraint->exactMessage : $constraint->maxMessage)
                 ->setParameter('{{ value }}', $this->formatValue($stringValue))
diff --git a/src/Symfony/Component/VarDumper/Caster/ReflectionCaster.php b/src/Symfony/Component/VarDumper/Caster/ReflectionCaster.php
index 45bd5e6ddf..c301df3622 100644
--- a/src/Symfony/Component/VarDumper/Caster/ReflectionCaster.php
+++ b/src/Symfony/Component/VarDumper/Caster/ReflectionCaster.php
@@ -376,6 +376,10 @@ class ReflectionCaster
     private static function addMap(array &$a, \Reflector $c, array $map, string $prefix = Caster::PREFIX_VIRTUAL)
     {
         foreach ($map as $k => $m) {
+            if (\PHP_VERSION_ID >= 80000 && 'isDisabled' === $k) {
+                continue;
+            }
+
             if (method_exists($c, $m) && false !== ($m = $c->$m()) && null !== $m) {
                 $a[$prefix.$k] = $m instanceof \Reflector ? $m->name : $m;
             }