diff --git a/src/Symfony/Component/Config/Builder/ClassBuilder.php b/src/Symfony/Component/Config/Builder/ClassBuilder.php
index 9bf503ec5c..7e4f3a4972 100644
--- a/src/Symfony/Component/Config/Builder/ClassBuilder.php
+++ b/src/Symfony/Component/Config/Builder/ClassBuilder.php
@@ -32,6 +32,7 @@ class ClassBuilder
     /** @var Method[] */
     private $methods = [];
     private $require = [];
+    private $use = [];
     private $implements = [];
 
     public function __construct(string $namespace, string $name)
@@ -66,6 +67,10 @@ class ClassBuilder
             }
             $require .= sprintf('require_once __DIR__.\DIRECTORY_SEPARATOR.\'%s\';', implode('\'.\DIRECTORY_SEPARATOR.\'', $path))."\n";
         }
+        $use = '';
+        foreach (array_keys($this->use) as $statement) {
+            $use .= sprintf('use %s;', $statement)."\n";
+        }
 
         $implements = [] === $this->implements ? '' : 'implements '.implode(', ', $this->implements);
         $body = '';
@@ -84,6 +89,7 @@ class ClassBuilder
 namespace NAMESPACE;
 
 REQUIRE
+USE
 
 /**
  * This class is automatically generated to help creating config.
@@ -94,17 +100,22 @@ class CLASS IMPLEMENTS
 {
 BODY
 }
-', ['NAMESPACE' => $this->namespace, 'REQUIRE' => $require, 'CLASS' => $this->getName(), 'IMPLEMENTS' => $implements, 'BODY' => $body]);
+', ['NAMESPACE' => $this->namespace, 'REQUIRE' => $require, 'USE' => $use, 'CLASS' => $this->getName(), 'IMPLEMENTS' => $implements, 'BODY' => $body]);
 
         return $content;
     }
 
-    public function addRequire(self $class)
+    public function addRequire(self $class): void
     {
         $this->require[] = $class;
     }
 
-    public function addImplements(string $interface)
+    public function addUse(string $class): void
+    {
+        $this->use[$class] = true;
+    }
+
+    public function addImplements(string $interface): void
     {
         $this->implements[] = '\\'.ltrim($interface, '\\');
     }
@@ -148,7 +159,7 @@ BODY
         return $this->namespace;
     }
 
-    public function getFqcn()
+    public function getFqcn(): string
     {
         return '\\'.$this->namespace.'\\'.$this->name;
     }
diff --git a/src/Symfony/Component/Config/Builder/ConfigBuilderGenerator.php b/src/Symfony/Component/Config/Builder/ConfigBuilderGenerator.php
index 63b309d786..fc36bb5feb 100644
--- a/src/Symfony/Component/Config/Builder/ConfigBuilderGenerator.php
+++ b/src/Symfony/Component/Config/Builder/ConfigBuilderGenerator.php
@@ -15,12 +15,14 @@ use Symfony\Component\Config\Definition\ArrayNode;
 use Symfony\Component\Config\Definition\BooleanNode;
 use Symfony\Component\Config\Definition\ConfigurationInterface;
 use Symfony\Component\Config\Definition\EnumNode;
+use Symfony\Component\Config\Definition\Exception\InvalidConfigurationException;
 use Symfony\Component\Config\Definition\FloatNode;
 use Symfony\Component\Config\Definition\IntegerNode;
 use Symfony\Component\Config\Definition\NodeInterface;
 use Symfony\Component\Config\Definition\PrototypedArrayNode;
 use Symfony\Component\Config\Definition\ScalarNode;
 use Symfony\Component\Config\Definition\VariableNode;
+use Symfony\Component\Config\Loader\ParamConfigurator;
 
 /**
  * Generate ConfigBuilders to help create valid config.
@@ -83,7 +85,7 @@ public function NAME(): string
         return $directory.\DIRECTORY_SEPARATOR.$class->getFilename();
     }
 
-    private function writeClasses()
+    private function writeClasses(): void
     {
         foreach ($this->classes as $class) {
             $this->buildConstructor($class);
@@ -95,7 +97,7 @@ public function NAME(): string
         $this->classes = [];
     }
 
-    private function buildNode(NodeInterface $node, ClassBuilder $class, string $namespace)
+    private function buildNode(NodeInterface $node, ClassBuilder $class, string $namespace): void
     {
         if (!$node instanceof ArrayNode) {
             throw new \LogicException('The node was expected to be an ArrayNode. This Configuration includes an edge case not supported yet.');
@@ -121,7 +123,7 @@ public function NAME(): string
         }
     }
 
-    private function handleArrayNode(ArrayNode $node, ClassBuilder $class, string $namespace)
+    private function handleArrayNode(ArrayNode $node, ClassBuilder $class, string $namespace): void
     {
         $childClass = new ClassBuilder($namespace, $node->getName());
         $class->addRequire($childClass);
@@ -134,20 +136,22 @@ public function NAME(array $value = []): CLASS
     if (null === $this->PROPERTY) {
         $this->PROPERTY = new CLASS($value);
     } elseif ([] !== $value) {
-        throw new \Symfony\Component\Config\Definition\Exception\InvalidConfigurationException(sprintf(\'The node created by "NAME()" has already been initialized. You cannot pass values the second time you call NAME().\'));
+        throw new InvalidConfigurationException(sprintf(\'The node created by "NAME()" has already been initialized. You cannot pass values the second time you call NAME().\'));
     }
 
     return $this->PROPERTY;
 }';
+        $class->addUse(InvalidConfigurationException::class);
         $class->addMethod($node->getName(), $body, ['PROPERTY' => $property->getName(), 'CLASS' => $childClass->getFqcn()]);
 
         $this->buildNode($node, $childClass, $this->getSubNamespace($childClass));
     }
 
-    private function handleVariableNode(VariableNode $node, ClassBuilder $class)
+    private function handleVariableNode(VariableNode $node, ClassBuilder $class): void
     {
         $comment = $this->getComment($node);
         $property = $class->addProperty($node->getName());
+        $class->addUse(ParamConfigurator::class);
 
         $body = '
 /**
@@ -162,7 +166,7 @@ public function NAME($valueDEFAULT): self
         $class->addMethod($node->getName(), $body, ['PROPERTY' => $property->getName(),  'COMMENT' => $comment, 'DEFAULT' => $node->hasDefaultValue() ? ' = '.var_export($node->getDefaultValue(), true) : '']);
     }
 
-    private function handlePrototypedArrayNode(PrototypedArrayNode $node, ClassBuilder $class, string $namespace)
+    private function handlePrototypedArrayNode(PrototypedArrayNode $node, ClassBuilder $class, string $namespace): void
     {
         $name = $this->getSingularName($node);
         $prototype = $node->getPrototype();
@@ -170,15 +174,16 @@ public function NAME($valueDEFAULT): self
 
         $parameterType = $this->getParameterType($prototype);
         if (null !== $parameterType || $prototype instanceof ScalarNode) {
+            $class->addUse(ParamConfigurator::class);
             $property = $class->addProperty($node->getName());
             if (null === $key = $node->getKeyAttribute()) {
                 // This is an array of values; don't use singular name
                 $body = '
 /**
- * @param list<TYPE> $value
+ * @param ParamConfigurator|list<TYPE|ParamConfigurator> $value
  * @return $this
  */
-public function NAME(array $value): self
+public function NAME($value): self
 {
     $this->PROPERTY = $value;
 
@@ -189,16 +194,17 @@ public function NAME(array $value): self
             } else {
                 $body = '
 /**
+ * @param ParamConfigurator|TYPE $value
  * @return $this
  */
-public function NAME(string $VAR, TYPE$VALUE): self
+public function NAME(string $VAR, $VALUE): self
 {
     $this->PROPERTY[$VAR] = $VALUE;
 
     return $this;
 }';
 
-                $class->addMethod($methodName, $body, ['PROPERTY' => $property->getName(), 'TYPE' => '' === $parameterType ? '' : $parameterType.' ', 'VAR' => '' === $key ? 'key' : $key, 'VALUE' => 'value' === $key ? 'data' : 'value']);
+                $class->addMethod($methodName, $body, ['PROPERTY' => $property->getName(), 'TYPE' => '' === $parameterType ? 'mixed' : $parameterType, 'VAR' => '' === $key ? 'key' : $key, 'VALUE' => 'value' === $key ? 'data' : 'value']);
             }
 
             return;
@@ -227,31 +233,33 @@ public function NAME(string $VAR, array $VALUE = []): CLASS
         return $this->PROPERTY[$VAR];
     }
 
-    throw new \Symfony\Component\Config\Definition\Exception\InvalidConfigurationException(sprintf(\'The node created by "NAME()" has already been initialized. You cannot pass values the second time you call NAME().\'));
+    throw new InvalidConfigurationException(sprintf(\'The node created by "NAME()" has already been initialized. You cannot pass values the second time you call NAME().\'));
 }';
+            $class->addUse(InvalidConfigurationException::class);
             $class->addMethod($methodName, $body, ['PROPERTY' => $property->getName(), 'CLASS' => $childClass->getFqcn(), 'VAR' => '' === $key ? 'key' : $key, 'VALUE' => 'value' === $key ? 'data' : 'value']);
         }
 
         $this->buildNode($prototype, $childClass, $namespace.'\\'.$childClass->getName());
     }
 
-    private function handleScalarNode(ScalarNode $node, ClassBuilder $class)
+    private function handleScalarNode(ScalarNode $node, ClassBuilder $class): void
     {
         $comment = $this->getComment($node);
         $property = $class->addProperty($node->getName());
+        $class->addUse(ParamConfigurator::class);
 
         $body = '
 /**
 COMMENT * @return $this
  */
-public function NAME(TYPE$value): self
+public function NAME($value): self
 {
     $this->PROPERTY = $value;
 
     return $this;
 }';
-        $parameterType = $this->getParameterType($node) ?? '';
-        $class->addMethod($node->getName(), $body, ['PROPERTY' => $property->getName(), 'TYPE' => '' === $parameterType ? '' : $parameterType.' ', 'COMMENT' => $comment]);
+
+        $class->addMethod($node->getName(), $body, ['PROPERTY' => $property->getName(), 'COMMENT' => $comment]);
     }
 
     private function getParameterType(NodeInterface $node): ?string
@@ -301,9 +309,15 @@ public function NAME(TYPE$value): self
         }
 
         if ($node instanceof EnumNode) {
-            $comment .= sprintf(' * @param %s $value', implode('|', array_map(function ($a) {
+            $comment .= sprintf(' * @param ParamConfigurator|%s $value', implode('|', array_map(function ($a) {
                 return var_export($a, true);
             }, $node->getValues()))).\PHP_EOL;
+        } else {
+            $parameterType = $this->getParameterType($node);
+            if (null === $parameterType || '' === $parameterType) {
+                $parameterType = 'mixed';
+            }
+            $comment .= ' * @param ParamConfigurator|'.$parameterType.' $value'.\PHP_EOL;
         }
 
         if ($node->isDeprecated()) {
@@ -387,9 +401,10 @@ public function NAME(): array
 
         $body .= '
     if ($value !== []) {
-        throw new \Symfony\Component\Config\Definition\Exception\InvalidConfigurationException(sprintf(\'The following keys are not supported by "%s": \', __CLASS__) . implode(\', \', array_keys($value)));
+        throw new InvalidConfigurationException(sprintf(\'The following keys are not supported by "%s": \', __CLASS__) . implode(\', \', array_keys($value)));
     }';
 
+        $class->addUse(InvalidConfigurationException::class);
         $class->addMethod('__construct', '
 public function __construct(array $value = [])
 {
diff --git a/src/Symfony/Component/Config/Loader/ParamConfigurator.php b/src/Symfony/Component/Config/Loader/ParamConfigurator.php
new file mode 100644
index 0000000000..70c3f79a68
--- /dev/null
+++ b/src/Symfony/Component/Config/Loader/ParamConfigurator.php
@@ -0,0 +1,32 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Config\Loader;
+
+/**
+ * Placeholder for a parameter.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+class ParamConfigurator
+{
+    private $name;
+
+    public function __construct(string $name)
+    {
+        $this->name = $name;
+    }
+
+    public function __toString(): string
+    {
+        return '%'.$this->name.'%';
+    }
+}
diff --git a/src/Symfony/Component/Config/Tests/Builder/Fixtures/Placeholders.config.php b/src/Symfony/Component/Config/Tests/Builder/Fixtures/Placeholders.config.php
new file mode 100644
index 0000000000..3423f9466d
--- /dev/null
+++ b/src/Symfony/Component/Config/Tests/Builder/Fixtures/Placeholders.config.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Symfony\Component\DependencyInjection\Loader\Configurator;
+use Symfony\Config\PlaceholdersConfig;
+
+return static function (PlaceholdersConfig $config) {
+    $config->enabled(env('FOO_ENABLED')->bool());
+    $config->favoriteFloat(param('eulers_number'));
+    $config->goodIntegers(env('MY_INTEGERS')->json());
+};
diff --git a/src/Symfony/Component/Config/Tests/Builder/Fixtures/Placeholders.output.php b/src/Symfony/Component/Config/Tests/Builder/Fixtures/Placeholders.output.php
new file mode 100644
index 0000000000..ca27298c36
--- /dev/null
+++ b/src/Symfony/Component/Config/Tests/Builder/Fixtures/Placeholders.output.php
@@ -0,0 +1,7 @@
+<?php
+
+return [
+    'enabled' => '%env(bool:FOO_ENABLED)%',
+    'favorite_float' => '%eulers_number%',
+    'good_integers' => '%env(json:MY_INTEGERS)%',
+];
diff --git a/src/Symfony/Component/Config/Tests/Builder/Fixtures/Placeholders.php b/src/Symfony/Component/Config/Tests/Builder/Fixtures/Placeholders.php
new file mode 100644
index 0000000000..78baa47735
--- /dev/null
+++ b/src/Symfony/Component/Config/Tests/Builder/Fixtures/Placeholders.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace Symfony\Component\Config\Tests\Builder\Fixtures;
+
+use Symfony\Component\Config\Definition\Builder\TreeBuilder;
+use Symfony\Component\Config\Definition\ConfigurationInterface;
+
+class Placeholders implements ConfigurationInterface
+{
+    public function getConfigTreeBuilder(): TreeBuilder
+    {
+        $tb = new TreeBuilder('placeholders');
+        $rootNode = $tb->getRootNode();
+        $rootNode
+            ->children()
+                ->booleanNode('enabled')->defaultFalse()->end()
+                ->floatNode('favorite_float')->end()
+                 ->arrayNode('good_integers')
+                    ->integerPrototype()->end()
+                ->end()
+            ->end()
+        ;
+
+        return $tb;
+    }
+}
diff --git a/src/Symfony/Component/Config/Tests/Builder/GeneratedConfigTest.php b/src/Symfony/Component/Config/Tests/Builder/GeneratedConfigTest.php
index c033d70086..4c0ace8d01 100644
--- a/src/Symfony/Component/Config/Tests/Builder/GeneratedConfigTest.php
+++ b/src/Symfony/Component/Config/Tests/Builder/GeneratedConfigTest.php
@@ -9,6 +9,8 @@ use Symfony\Component\Config\Builder\ConfigBuilderInterface;
 use Symfony\Component\Config\Definition\Exception\InvalidConfigurationException;
 use Symfony\Component\Config\Tests\Builder\Fixtures\AddToList;
 use Symfony\Component\Config\Tests\Builder\Fixtures\NodeInitialValues;
+use Symfony\Component\DependencyInjection\Loader\Configurator\AbstractConfigurator;
+use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
 use Symfony\Config\AddToListConfig;
 
 /**
@@ -30,6 +32,14 @@ class GeneratedConfigTest extends TestCase
         foreach ($array as $name => $alias) {
             yield $name => [$name, $alias];
         }
+
+        /*
+         * Force load ContainerConfigurator to make env(), param() etc available
+         * and also check if symfony/dependency-injection is installed
+         */
+        if (class_exists(ContainerConfigurator::class)) {
+            yield 'Placeholders' => ['Placeholders', 'placeholders'];
+        }
     }
 
     /**
@@ -45,7 +55,11 @@ class GeneratedConfigTest extends TestCase
 
         $this->assertInstanceOf(ConfigBuilderInterface::class, $configBuilder);
         $this->assertSame($alias, $configBuilder->getExtensionAlias());
-        $this->assertSame($expectedOutput, $configBuilder->toArray());
+        $output = $configBuilder->toArray();
+        if (class_exists(AbstractConfigurator::class)) {
+            $output = AbstractConfigurator::processValue($output);
+        }
+        $this->assertSame($expectedOutput, $output);
     }
 
     /**
diff --git a/src/Symfony/Component/DependencyInjection/Loader/Configurator/AbstractConfigurator.php b/src/Symfony/Component/DependencyInjection/Loader/Configurator/AbstractConfigurator.php
index 93d84337d0..788d2459d7 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/Configurator/AbstractConfigurator.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/Configurator/AbstractConfigurator.php
@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\DependencyInjection\Loader\Configurator;
 
+use Symfony\Component\Config\Loader\ParamConfigurator;
 use Symfony\Component\DependencyInjection\Argument\AbstractArgument;
 use Symfony\Component\DependencyInjection\Argument\ArgumentInterface;
 use Symfony\Component\DependencyInjection\Definition;
@@ -83,7 +84,7 @@ abstract class AbstractConfigurator
             return $def;
         }
 
-        if ($value instanceof EnvConfigurator) {
+        if ($value instanceof ParamConfigurator) {
             return (string) $value;
         }
 
diff --git a/src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php b/src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php
index 0cafaa2037..9ea1dfec4d 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php
@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\DependencyInjection\Loader\Configurator;
 
+use Symfony\Component\Config\Loader\ParamConfigurator;
 use Symfony\Component\DependencyInjection\Argument\AbstractArgument;
 use Symfony\Component\DependencyInjection\Argument\IteratorArgument;
 use Symfony\Component\DependencyInjection\Argument\ServiceLocatorArgument;
@@ -96,9 +97,9 @@ class ContainerConfigurator extends AbstractConfigurator
 /**
  * Creates a parameter.
  */
-function param(string $name): string
+function param(string $name): ParamConfigurator
 {
-    return '%'.$name.'%';
+    return new ParamConfigurator($name);
 }
 
 /**
diff --git a/src/Symfony/Component/DependencyInjection/Loader/Configurator/EnvConfigurator.php b/src/Symfony/Component/DependencyInjection/Loader/Configurator/EnvConfigurator.php
index 21d9b84df1..d1864f564a 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/Configurator/EnvConfigurator.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/Configurator/EnvConfigurator.php
@@ -11,7 +11,9 @@
 
 namespace Symfony\Component\DependencyInjection\Loader\Configurator;
 
-class EnvConfigurator
+use Symfony\Component\Config\Loader\ParamConfigurator;
+
+class EnvConfigurator extends ParamConfigurator
 {
     /**
      * @var string[]
@@ -23,10 +25,7 @@ class EnvConfigurator
         $this->stack = explode(':', $name);
     }
 
-    /**
-     * @return string
-     */
-    public function __toString()
+    public function __toString(): string
     {
         return '%env('.implode(':', $this->stack).')%';
     }
diff --git a/src/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php
index f10aaac4a1..a777653140 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php
@@ -128,6 +128,9 @@ class PhpFileLoader extends FileLoader
             }
         }
 
+        // Force load ContainerConfigurator to make env(), param() etc available.
+        class_exists(ContainerConfigurator::class);
+
         $callback(...$arguments);
 
         /** @var ConfigBuilderInterface $configBuilder */