diff --git a/src/Symfony/Bridge/ProxyManager/LazyProxy/PhpDumper/ProxyDumper.php b/src/Symfony/Bridge/ProxyManager/LazyProxy/PhpDumper/ProxyDumper.php
index 85628aee93..ed12685d2a 100644
--- a/src/Symfony/Bridge/ProxyManager/LazyProxy/PhpDumper/ProxyDumper.php
+++ b/src/Symfony/Bridge/ProxyManager/LazyProxy/PhpDumper/ProxyDumper.php
@@ -85,6 +85,7 @@ EOF;
     public function getProxyCode(Definition $definition)
     {
         $code = $this->classGenerator->generate($this->generateProxyClass($definition));
+        $code = preg_replace('/^(class [^ ]++ extends )([^\\\\])/', '$1\\\\$2', $code);
 
         if (version_compare(self::getProxyManagerVersion(), '2.2', '<')) {
             $code = preg_replace(
diff --git a/src/Symfony/Bridge/ProxyManager/Tests/LazyProxy/Fixtures/php/lazy_service_structure.txt b/src/Symfony/Bridge/ProxyManager/Tests/LazyProxy/Fixtures/php/lazy_service_structure.txt
index 574041b89b..906fff68f7 100644
--- a/src/Symfony/Bridge/ProxyManager/Tests/LazyProxy/Fixtures/php/lazy_service_structure.txt
+++ b/src/Symfony/Bridge/ProxyManager/Tests/LazyProxy/Fixtures/php/lazy_service_structure.txt
@@ -21,5 +21,5 @@ class LazyServiceProjectServiceContainer extends Container
     }
 }
 
-class stdClass_%s extends %SstdClass implements \ProxyManager\%s
+class stdClass_%s extends \stdClass implements \ProxyManager\%s
 {%a}%A
diff --git a/src/Symfony/Component/DependencyInjection/Extension/Extension.php b/src/Symfony/Component/DependencyInjection/Extension/Extension.php
index 925775aa56..5f855357d7 100644
--- a/src/Symfony/Component/DependencyInjection/Extension/Extension.php
+++ b/src/Symfony/Component/DependencyInjection/Extension/Extension.php
@@ -80,6 +80,11 @@ abstract class Extension implements ExtensionInterface, ConfigurationExtensionIn
     public function getConfiguration(array $config, ContainerBuilder $container)
     {
         $class = \get_class($this);
+
+        if (false !== strpos($class, "\0")) {
+            return null; // ignore anonymous classes
+        }
+
         $class = substr_replace($class, '\Configuration', strrpos($class, '\\'));
         $class = $container->getReflectionClass($class);
 
diff --git a/src/Symfony/Component/Dotenv/Dotenv.php b/src/Symfony/Component/Dotenv/Dotenv.php
index 613d9f8246..14cd5a6858 100644
--- a/src/Symfony/Component/Dotenv/Dotenv.php
+++ b/src/Symfony/Component/Dotenv/Dotenv.php
@@ -458,7 +458,7 @@ final class Dotenv
             } elseif (isset($this->values[$name])) {
                 $value = $this->values[$name];
             } else {
-                $value = '';
+                $value = (string) getenv($name);
             }
 
             if (!$matches['opening_brace'] && isset($matches['closing_brace'])) {
diff --git a/src/Symfony/Component/Dotenv/Tests/DotenvTest.php b/src/Symfony/Component/Dotenv/Tests/DotenvTest.php
index e2b387ebc4..0b272a00e8 100644
--- a/src/Symfony/Component/Dotenv/Tests/DotenvTest.php
+++ b/src/Symfony/Component/Dotenv/Tests/DotenvTest.php
@@ -431,6 +431,17 @@ class DotenvTest extends TestCase
         }
     }
 
+    public function testGetVariablesValueFromGetenv()
+    {
+        putenv('Foo=Bar');
+
+        $dotenv = new Dotenv(true);
+        $values = $dotenv->parse('Foo=${Foo}');
+        $this->assertSame('Bar', $values['Foo']);
+
+        putenv('Foo');
+    }
+
     /**
      * @group legacy
      * @expectedDeprecation The default value of "$usePutenv" argument of "%s" will be changed from "true" to "false" in Symfony 5.0. You should define its value explicitly.
diff --git a/src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php b/src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php
index 202f3a5a6a..a2a7e01854 100644
--- a/src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php
+++ b/src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php
@@ -403,13 +403,11 @@ class NativeSessionStorage implements SessionStorageInterface
      *     ini_set('session.save_path', '/tmp');
      *
      * or pass in a \SessionHandler instance which configures session.save_handler in the
-     * constructor, for a template see NativeFileSessionHandler or use handlers in
-     * composer package drak/native-session
+     * constructor, for a template see NativeFileSessionHandler.
      *
      * @see https://php.net/session-set-save-handler
      * @see https://php.net/sessionhandlerinterface
      * @see https://php.net/sessionhandler
-     * @see https://github.com/zikula/NativeSession
      *
      * @param \SessionHandlerInterface|null $saveHandler
      *