diff --git a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
index d3d10fd97f..72d66442c6 100644
--- a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
+++ b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
@@ -36,6 +36,7 @@ use Symfony\Component\DependencyInjection\ChildDefinition;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\DependencyInjection\Definition;
+use Symfony\Component\DependencyInjection\EnvVarProcessorInterface;
 use Symfony\Component\DependencyInjection\Exception\LogicException;
 use Symfony\Component\DependencyInjection\Loader\XmlFileLoader;
 use Symfony\Component\DependencyInjection\Reference;
@@ -283,6 +284,8 @@ class FrameworkExtension extends Extension
             ->addTag('console.command');
         $container->registerForAutoconfiguration(ResourceCheckerInterface::class)
             ->addTag('config_cache.resource_checker');
+        $container->registerForAutoconfiguration(EnvVarProcessorInterface::class)
+            ->addTag('container.env_var_processor');
         $container->registerForAutoconfiguration(ServiceSubscriberInterface::class)
             ->addTag('container.service_subscriber');
         $container->registerForAutoconfiguration(ArgumentValueResolverInterface::class)
diff --git a/src/Symfony/Component/DependencyInjection/CHANGELOG.md b/src/Symfony/Component/DependencyInjection/CHANGELOG.md
index 4232369e2e..09bc2ce361 100644
--- a/src/Symfony/Component/DependencyInjection/CHANGELOG.md
+++ b/src/Symfony/Component/DependencyInjection/CHANGELOG.md
@@ -4,6 +4,7 @@ CHANGELOG
 3.4.0
 -----
 
+ * added `EnvVarProcessorInterface` and corresponding "container.env_var_processor" tag for processing env vars
  * added support for ignore-on-uninitialized references
  * deprecated service auto-registration while autowiring
  * deprecated the ability to check for the initialization of a private service with the `Container::initialized()` method
diff --git a/src/Symfony/Component/DependencyInjection/Compiler/PassConfig.php b/src/Symfony/Component/DependencyInjection/Compiler/PassConfig.php
index 184c7b25a0..63659ed892 100644
--- a/src/Symfony/Component/DependencyInjection/Compiler/PassConfig.php
+++ b/src/Symfony/Component/DependencyInjection/Compiler/PassConfig.php
@@ -43,6 +43,7 @@ class PassConfig
             100 => array(
                 $resolveClassPass = new ResolveClassPass(),
                 new ResolveInstanceofConditionalsPass(),
+                new RegisterEnvVarProcessorsPass(),
             ),
         );
 
diff --git a/src/Symfony/Component/DependencyInjection/Compiler/RegisterEnvVarProcessorsPass.php b/src/Symfony/Component/DependencyInjection/Compiler/RegisterEnvVarProcessorsPass.php
new file mode 100644
index 0000000000..247f5b69ad
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Compiler/RegisterEnvVarProcessorsPass.php
@@ -0,0 +1,72 @@
+<?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\DependencyInjection\Compiler;
+
+use Symfony\Component\DependencyInjection\Argument\ServiceClosureArgument;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\EnvVarProcessorInterface;
+use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
+use Symfony\Component\DependencyInjection\ParameterBag\EnvPlaceholderParameterBag;
+use Symfony\Component\DependencyInjection\ServiceLocator;
+use Symfony\Component\DependencyInjection\Reference;
+
+/**
+ * Creates the container.env_var_processors_locator service.
+ *
+ * @author Nicolas Grekas <p@tchwork.com>
+ */
+class RegisterEnvVarProcessorsPass implements CompilerPassInterface
+{
+    private static $allowedTypes = array('array', 'bool', 'float', 'int', 'string');
+
+    public function process(ContainerBuilder $container)
+    {
+        $bag = $container->getParameterBag();
+        $types = array();
+        $processors = array();
+        foreach ($container->findTaggedServiceIds('container.env_var_processor') as $id => $tags) {
+            foreach ($tags as $attr) {
+                if (!$r = $container->getReflectionClass($class = $container->getDefinition($id)->getClass())) {
+                    throw new InvalidArgumentException(sprintf('Class "%s" used for service "%s" cannot be found.', $class, $id));
+                } elseif (!$r->isSubclassOf(EnvVarProcessorInterface::class)) {
+                    throw new InvalidArgumentException(sprintf('Service "%s" must implement interface "%s".', $id, EnvVarProcessorInterface::class));
+                }
+                foreach ($class::getProvidedTypes() as $prefix => $type) {
+                    $processors[$prefix] = new ServiceClosureArgument(new Reference($id));
+                    $types[$prefix] = self::validateProvidedTypes($type, $class);
+                }
+            }
+        }
+
+        if ($processors) {
+            if ($bag instanceof EnvPlaceholderParameterBag) {
+                $bag->setProvidedTypes($types);
+            }
+            $container->register('container.env_var_processors_locator', ServiceLocator::class)
+                ->setArguments(array($processors))
+            ;
+        }
+    }
+
+    private static function validateProvidedTypes($types, $class)
+    {
+        $types = explode('|', $types);
+
+        foreach ($types as $type) {
+            if (!in_array($type, self::$allowedTypes)) {
+                throw new InvalidArgumentException(sprintf('Invalid type "%s" returned by "%s::getProvidedTypes()", expected one of "%s".', $type, $class, implode('", "', self::$allowedTypes)));
+            }
+        }
+
+        return $types;
+    }
+}
diff --git a/src/Symfony/Component/DependencyInjection/Container.php b/src/Symfony/Component/DependencyInjection/Container.php
index ac423bd4a4..75ba8a2bdb 100644
--- a/src/Symfony/Component/DependencyInjection/Container.php
+++ b/src/Symfony/Component/DependencyInjection/Container.php
@@ -13,6 +13,7 @@ namespace Symfony\Component\DependencyInjection;
 
 use Symfony\Component\DependencyInjection\Exception\EnvNotFoundException;
 use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
+use Symfony\Component\DependencyInjection\Exception\ParameterCircularReferenceException;
 use Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException;
 use Symfony\Component\DependencyInjection\Exception\ServiceCircularReferenceException;
 use Symfony\Component\DependencyInjection\ParameterBag\ParameterBagInterface;
@@ -48,6 +49,7 @@ class Container implements ResettableContainerInterface
     protected $methodMap = array();
     protected $aliases = array();
     protected $loading = array();
+    protected $resolving = array();
 
     /**
      * @internal
@@ -62,6 +64,7 @@ class Container implements ResettableContainerInterface
     private $underscoreMap = array('_' => '', '.' => '_', '\\' => '_');
     private $envCache = array();
     private $compiled = false;
+    private $getEnv;
 
     /**
      * @param ParameterBagInterface $parameterBag A ParameterBagInterface instance
@@ -438,23 +441,37 @@ class Container implements ResettableContainerInterface
      */
     protected function getEnv($name)
     {
+        if (isset($this->resolving[$envName = "env($name)"])) {
+            throw new ParameterCircularReferenceException(array_keys($this->resolving));
+        }
         if (isset($this->envCache[$name]) || array_key_exists($name, $this->envCache)) {
             return $this->envCache[$name];
         }
-        if (isset($_SERVER[$name]) && 0 !== strpos($name, 'HTTP_')) {
-            return $this->envCache[$name] = $_SERVER[$name];
+        if (!$this->has($id = 'container.env_var_processors_locator')) {
+            $this->set($id, new ServiceLocator(array()));
         }
-        if (isset($_ENV[$name])) {
-            return $this->envCache[$name] = $_ENV[$name];
-        }
-        if (false !== ($env = getenv($name)) && null !== $env) { // null is a possible value because of thread safety issues
-            return $this->envCache[$name] = $env;
-        }
-        if (!$this->hasParameter("env($name)")) {
-            throw new EnvNotFoundException($name);
+        if (!$this->getEnv) {
+            $this->getEnv = new \ReflectionMethod($this, __FUNCTION__);
+            $this->getEnv->setAccessible(true);
+            $this->getEnv = $this->getEnv->getClosure($this);
         }
+        $processors = $this->get($id);
 
-        return $this->envCache[$name] = $this->getParameter("env($name)");
+        if (false !== $i = strpos($name, ':')) {
+            $prefix = substr($name, 0, $i);
+            $localName = substr($name, 1 + $i);
+        } else {
+            $prefix = 'string';
+            $localName = $name;
+        }
+        $processor = $processors->has($prefix) ? $processors->get($prefix) : new EnvVarProcessor($this);
+
+        $this->resolving[$envName] = true;
+        try {
+            return $this->envCache[$name] = $processor->getEnv($prefix, $localName, $this->getEnv);
+        } finally {
+            unset($this->resolving[$envName]);
+        }
     }
 
     /**
diff --git a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
index 2b8dfd6a3e..63a7c2b331 100644
--- a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
+++ b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
@@ -1472,20 +1472,26 @@ class ContainerBuilder extends Container implements TaggedContainerInterface
     protected function getEnv($name)
     {
         $value = parent::getEnv($name);
+        $bag = $this->getParameterBag();
 
-        if (!is_string($value) || !$this->getParameterBag() instanceof EnvPlaceholderParameterBag) {
+        if (!is_string($value) || !$bag instanceof EnvPlaceholderParameterBag) {
             return $value;
         }
 
-        foreach ($this->getParameterBag()->getEnvPlaceholders() as $env => $placeholders) {
+        foreach ($bag->getEnvPlaceholders() as $env => $placeholders) {
             if (isset($placeholders[$value])) {
-                $bag = new ParameterBag($this->getParameterBag()->all());
+                $bag = new ParameterBag($bag->all());
 
                 return $bag->unescapeValue($bag->get("env($name)"));
             }
         }
 
-        return $value;
+        $this->resolving["env($name)"] = true;
+        try {
+            return $bag->unescapeValue($this->resolveEnvPlaceholders($bag->escapeValue($value), true));
+        } finally {
+            unset($this->resolving["env($name)"]);
+        }
     }
 
     /**
diff --git a/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php b/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php
index 2f70d59d81..87835ee440 100644
--- a/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php
+++ b/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php
@@ -1112,7 +1112,7 @@ EOF;
             $export = $this->exportParameters(array($value));
             $export = explode('0 => ', substr(rtrim($export, " )\n"), 7, -1), 2);
 
-            if (preg_match("/\\\$this->(?:getEnv\('\w++'\)|targetDirs\[\d++\])/", $export[1])) {
+            if (preg_match("/\\\$this->(?:getEnv\('(?:\w++:)*+\w++'\)|targetDirs\[\d++\])/", $export[1])) {
                 $dynamicPhp[$key] = sprintf('%scase %s: $value = %s; break;', $export[0], $this->export($key), $export[1]);
             } else {
                 $php[] = sprintf('%s%s => %s,', $export[0], $this->export($key), $export[1]);
@@ -1685,7 +1685,7 @@ EOF;
                 return $dumpedValue;
             }
 
-            if (!preg_match("/\\\$this->(?:getEnv\('\w++'\)|targetDirs\[\d++\])/", $dumpedValue)) {
+            if (!preg_match("/\\\$this->(?:getEnv\('(?:\w++:)*+\w++'\)|targetDirs\[\d++\])/", $dumpedValue)) {
                 return sprintf("\$this->parameters['%s']", $name);
             }
         }
@@ -1880,13 +1880,16 @@ EOF;
     {
         $export = var_export($value, true);
 
-        if ("'" === $export[0] && $export !== $resolvedExport = $this->container->resolveEnvPlaceholders($export, "'.\$this->getEnv('%s').'")) {
+        if ("'" === $export[0] && $export !== $resolvedExport = $this->container->resolveEnvPlaceholders($export, "'.\$this->getEnv('string:%s').'")) {
             $export = $resolvedExport;
-            if ("'" === $export[1]) {
-                $export = substr($export, 3);
-            }
             if (".''" === substr($export, -3)) {
                 $export = substr($export, 0, -3);
+                if ("'" === $export[1]) {
+                    $export = substr_replace($export, '', 18, 7);
+                }
+            }
+            if ("'" === $export[1]) {
+                $export = substr($export, 3);
             }
         }
 
diff --git a/src/Symfony/Component/DependencyInjection/EnvVarProcessor.php b/src/Symfony/Component/DependencyInjection/EnvVarProcessor.php
new file mode 100644
index 0000000000..51a19367e2
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/EnvVarProcessor.php
@@ -0,0 +1,160 @@
+<?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\DependencyInjection;
+
+use Symfony\Component\Config\Util\XmlUtils;
+use Symfony\Component\DependencyInjection\Exception\EnvNotFoundException;
+use Symfony\Component\DependencyInjection\Exception\RuntimeException;
+
+class EnvVarProcessor implements EnvVarProcessorInterface
+{
+    private $container;
+
+    public function __construct(ContainerInterface $container)
+    {
+        $this->container = $container;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public static function getProvidedTypes()
+    {
+        return array(
+            'base64' => 'string',
+            'bool' => 'bool',
+            'const' => 'bool|int|float|string|array',
+            'file' => 'string',
+            'float' => 'float',
+            'int' => 'int',
+            'json' => 'array',
+            'resolve' => 'string',
+            'string' => 'string',
+        );
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getEnv($prefix, $name, \Closure $getEnv)
+    {
+        $i = strpos($name, ':');
+
+        if ('file' === $prefix) {
+            if (!is_scalar($file = $getEnv($name))) {
+                throw new RuntimeException(sprintf('Invalid file name: env var "%s" is non-scalar.', $name));
+            }
+            if (!file_exists($file)) {
+                throw new RuntimeException(sprintf('Env "file:%s" not found: %s does not exist.', $name, $file));
+            }
+
+            return file_get_contents($file);
+        }
+
+        if (false !== $i || 'string' !== $prefix) {
+            if (null === $env = $getEnv($name)) {
+                return;
+            }
+        } elseif (isset($_SERVER[$name]) && 0 !== strpos($name, 'HTTP_')) {
+            $env = $_SERVER[$name];
+        } elseif (isset($_ENV[$name])) {
+            $env = $_ENV[$name];
+        } elseif (false === ($env = getenv($name)) || null === $env) { // null is a possible value because of thread safety issues
+            if (!$this->container->hasParameter("env($name)")) {
+                throw new EnvNotFoundException($name);
+            }
+
+            if (null === $env = $this->container->getParameter("env($name)")) {
+                return;
+            }
+        }
+
+        if (!is_scalar($env)) {
+            throw new RuntimeException(sprintf('Non-scalar env var "%s" cannot be cast to %s.', $name, $prefix));
+        }
+
+        if ('string' === $prefix) {
+            return (string) $env;
+        }
+
+        if ('bool' === $prefix) {
+            return (bool) self::phpize($env);
+        }
+
+        if ('int' === $prefix) {
+            if (!is_numeric($env = self::phpize($env))) {
+                throw new RuntimeException(sprintf('Non-numeric env var "%s" cannot be cast to int.', $name));
+            }
+
+            return (int) $env;
+        }
+
+        if ('float' === $prefix) {
+            if (!is_numeric($env = self::phpize($env))) {
+                throw new RuntimeException(sprintf('Non-numeric env var "%s" cannot be cast to float.', $name));
+            }
+
+            return (float) $env;
+        }
+
+        if ('const' === $prefix) {
+            if (!defined($env)) {
+                throw new RuntimeException(sprintf('Env var "%s" maps to undefined constant "%s".', $name, $env));
+            }
+
+            return constant($name);
+        }
+
+        if ('base64' === $prefix) {
+            return base64_decode($env);
+        }
+
+        if ('json' === $prefix) {
+            $env = json_decode($env, true, JSON_BIGINT_AS_STRING);
+
+            if (JSON_ERROR_NONE !== json_last_error()) {
+                throw new RuntimeException(sprintf('Invalid JSON in env var "%s": '.json_last_error_msg(), $name));
+            }
+
+            if (!is_array($env)) {
+                throw new RuntimeException(sprintf('Invalid JSON env var "%s": array expected, %s given.', $name, gettype($env)));
+            }
+
+            return $env;
+        }
+
+        if ('resolve' === $prefix) {
+            return preg_replace_callback('/%%|%([^%\s]+)%/', function ($match) use ($name) {
+                if (!isset($match[1])) {
+                    return '%';
+                }
+                $value = $this->container->getParameter($match[1]);
+                if (!is_scalar($value)) {
+                    throw new RuntimeException(sprintf('Parameter "%s" found when resolving env var "%s" must be scalar, "%s" given.', $match[1], $name, gettype($value)));
+                }
+
+                return $value;
+            }, $env);
+        }
+
+        throw new RuntimeException(sprintf('Unsupported env var prefix "%s".', $prefix));
+    }
+
+    private static function phpize($value)
+    {
+        if (!class_exists(XmlUtils::class)) {
+            throw new RuntimeException('The Symfony Config component is required to cast env vars to "bool", "int" or "float".');
+        }
+
+        return XmlUtils::phpize($value);
+    }
+}
diff --git a/src/Symfony/Component/DependencyInjection/EnvVarProcessorInterface.php b/src/Symfony/Component/DependencyInjection/EnvVarProcessorInterface.php
new file mode 100644
index 0000000000..fce9f5cd7a
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/EnvVarProcessorInterface.php
@@ -0,0 +1,38 @@
+<?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\DependencyInjection;
+
+/**
+ * The EnvVarProcessorInterface is implemented by objects that manage environment-like variables.
+ *
+ * @author Nicolas Grekas <p@tchwork.com>
+ */
+interface EnvVarProcessorInterface
+{
+    /**
+     * Returns the value of the given variable as managed by the current instance.
+     *
+     * @param string   $prefix The namespace of the variable
+     * @param string   $name   The name of the variable within the namespace
+     * @param \Closure $getEnv A closure that allows fetching more env vars
+     *
+     * @return mixed
+     *
+     * @throws RuntimeException on error
+     */
+    public function getEnv($prefix, $name, \Closure $getEnv);
+
+    /**
+     * @return string[] The PHP-types managed by getEnv(), keyed by prefixes
+     */
+    public static function getProvidedTypes();
+}
diff --git a/src/Symfony/Component/DependencyInjection/ParameterBag/EnvPlaceholderParameterBag.php b/src/Symfony/Component/DependencyInjection/ParameterBag/EnvPlaceholderParameterBag.php
index fd859068be..e0fe4c7cdf 100644
--- a/src/Symfony/Component/DependencyInjection/ParameterBag/EnvPlaceholderParameterBag.php
+++ b/src/Symfony/Component/DependencyInjection/ParameterBag/EnvPlaceholderParameterBag.php
@@ -20,6 +20,7 @@ use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
 class EnvPlaceholderParameterBag extends ParameterBag
 {
     private $envPlaceholders = array();
+    private $providedTypes = array();
 
     /**
      * {@inheritdoc}
@@ -34,7 +35,7 @@ class EnvPlaceholderParameterBag extends ParameterBag
                     return $placeholder; // return first result
                 }
             }
-            if (preg_match('/\W/', $env)) {
+            if (!preg_match('/^(?:\w++:)*+\w++$/', $env)) {
                 throw new InvalidArgumentException(sprintf('Invalid %s name: only "word" characters are allowed.', $name));
             }
 
@@ -80,6 +81,24 @@ class EnvPlaceholderParameterBag extends ParameterBag
         }
     }
 
+    /**
+     * Maps env prefixes to their corresponding PHP types.
+     */
+    public function setProvidedTypes(array $providedTypes)
+    {
+        $this->providedTypes = $providedTypes;
+    }
+
+    /**
+     * Gets the PHP types corresponding to env() parameter prefixes.
+     *
+     * @return string[][]
+     */
+    public function getProvidedTypes()
+    {
+        return $this->providedTypes;
+    }
+
     /**
      * {@inheritdoc}
      */
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Compiler/RegisterEnvVarProcessorsPassTest.php b/src/Symfony/Component/DependencyInjection/Tests/Compiler/RegisterEnvVarProcessorsPassTest.php
new file mode 100644
index 0000000000..dc3a1f1834
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Compiler/RegisterEnvVarProcessorsPassTest.php
@@ -0,0 +1,75 @@
+<?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\DependencyInjection\Tests\Compiler;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\DependencyInjection\Compiler\RegisterEnvVarProcessorsPass;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\EnvVarProcessorInterface;
+
+class RegisterEnvVarProcessorsPassTest extends TestCase
+{
+    public function testSimpleProcessor()
+    {
+        $container = new ContainerBuilder();
+        $container->register('foo', SimpleProcessor::class)->addTag('container.env_var_processor');
+
+        (new RegisterEnvVarProcessorsPass())->process($container);
+
+        $this->assertTrue($container->has('container.env_var_processors_locator'));
+        $this->assertInstanceof(SimpleProcessor::class, $container->get('container.env_var_processors_locator')->get('foo'));
+
+        $this->assertSame(array('foo' => array('string')), $container->getParameterBag()->getProvidedTypes());
+    }
+
+    public function testNoProcessor()
+    {
+        $container = new ContainerBuilder();
+
+        (new RegisterEnvVarProcessorsPass())->process($container);
+
+        $this->assertFalse($container->has('container.env_var_processors_locator'));
+    }
+
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\InvalidArgumentException
+     * @expectedExceptionMessage Invalid type "foo" returned by "Symfony\Component\DependencyInjection\Tests\Compiler\BadProcessor::getProvidedTypes()", expected one of "array", "bool", "float", "int", "string".
+     */
+    public function testBadProcessor()
+    {
+        $container = new ContainerBuilder();
+        $container->register('foo', BadProcessor::class)->addTag('container.env_var_processor');
+
+        (new RegisterEnvVarProcessorsPass())->process($container);
+    }
+}
+
+class SimpleProcessor implements EnvVarProcessorInterface
+{
+    public function getEnv($prefix, $name, \Closure $getEnv)
+    {
+        return $getEnv($name);
+    }
+
+    public static function getProvidedTypes()
+    {
+        return array('foo' => 'string');
+    }
+}
+
+class BadProcessor extends SimpleProcessor
+{
+    public static function getProvidedTypes()
+    {
+        return array('foo' => 'string|foo');
+    }
+}
diff --git a/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php b/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php
index 54e3227d23..d074189cbe 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php
@@ -665,6 +665,70 @@ class ContainerBuilderTest extends TestCase
         $container->compile(true);
     }
 
+    public function testDynamicEnv()
+    {
+        putenv('DUMMY_FOO=some%foo%');
+        putenv('DUMMY_BAR=%bar%');
+
+        $container = new ContainerBuilder();
+        $container->setParameter('foo', 'Foo%env(resolve:DUMMY_BAR)%');
+        $container->setParameter('bar', 'Bar');
+        $container->setParameter('baz', '%env(resolve:DUMMY_FOO)%');
+
+        $container->compile(true);
+        putenv('DUMMY_FOO');
+        putenv('DUMMY_BAR');
+
+        $this->assertSame('someFooBar', $container->getParameter('baz'));
+    }
+
+    public function testCastEnv()
+    {
+        $container = new ContainerBuilder();
+        $container->setParameter('env(FAKE)', '123');
+
+        $container->register('foo', 'stdClass')->setProperties(array(
+            'fake' => '%env(int:FAKE)%',
+        ));
+
+        $container->compile(true);
+
+        $this->assertSame(123, $container->get('foo')->fake);
+    }
+
+    public function testEnvAreNullable()
+    {
+        $container = new ContainerBuilder();
+        $container->setParameter('env(FAKE)', null);
+
+        $container->register('foo', 'stdClass')->setProperties(array(
+            'fake' => '%env(int:FAKE)%',
+        ));
+
+        $container->compile(true);
+
+        $this->assertNull($container->get('foo')->fake);
+    }
+
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\ParameterCircularReferenceException
+     * @expectedExceptionMessage Circular reference detected for parameter "env(resolve:DUMMY_ENV_VAR)" ("env(resolve:DUMMY_ENV_VAR)" > "env(resolve:DUMMY_ENV_VAR)").
+     */
+    public function testCircularDynamicEnv()
+    {
+        putenv('DUMMY_ENV_VAR=some%foo%');
+
+        $container = new ContainerBuilder();
+        $container->setParameter('foo', '%bar%');
+        $container->setParameter('bar', '%env(resolve:DUMMY_ENV_VAR)%');
+
+        try {
+            $container->compile(true);
+        } finally {
+            putenv('DUMMY_ENV_VAR');
+        }
+    }
+
     /**
      * @expectedException \LogicException
      */
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php b/src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php
index 62213ee280..ac8aee2fc5 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php
@@ -21,6 +21,7 @@ use Symfony\Component\DependencyInjection\Argument\ServiceClosureArgument;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\ContainerInterface as SymfonyContainerInterface;
 use Symfony\Component\DependencyInjection\Dumper\PhpDumper;
+use Symfony\Component\DependencyInjection\EnvVarProcessorInterface;
 use Symfony\Component\DependencyInjection\ParameterBag\ParameterBag;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\DependencyInjection\Tests\Fixtures\StubbedTranslator;
@@ -338,13 +339,82 @@ class PhpDumperTest extends TestCase
 
     public function testEnvParameter()
     {
+        $rand = mt_rand();
+        putenv('Baz='.$rand);
         $container = new ContainerBuilder();
         $loader = new YamlFileLoader($container, new FileLocator(self::$fixturesPath.'/yaml'));
         $loader->load('services26.yml');
+        $container->setParameter('env(json_file)', self::$fixturesPath.'/array.json');
         $container->compile();
         $dumper = new PhpDumper($container);
 
-        $this->assertStringEqualsFile(self::$fixturesPath.'/php/services26.php', $dumper->dump(), '->dump() dumps inline definitions which reference service_container');
+        $this->assertStringEqualsFile(self::$fixturesPath.'/php/services26.php', $dumper->dump(array('class' => 'Symfony_DI_PhpDumper_Test_EnvParameters', 'file' => self::$fixturesPath.'/php/services26.php')));
+
+        require self::$fixturesPath.'/php/services26.php';
+        $container = new \Symfony_DI_PhpDumper_Test_EnvParameters();
+        $this->assertSame($rand, $container->getParameter('baz'));
+        $this->assertSame(array(123, 'abc'), $container->getParameter('json'));
+        $this->assertSame('sqlite:///foo/bar/var/data.db', $container->getParameter('db_dsn'));
+        putenv('Baz');
+    }
+
+    public function testResolvedBase64EnvParameters()
+    {
+        $container = new ContainerBuilder();
+        $container->setParameter('env(foo)', base64_encode('world'));
+        $container->setParameter('hello', '%env(base64:foo)%');
+        $container->compile(true);
+
+        $expected = array(
+          'env(foo)' => 'd29ybGQ=',
+          'hello' => 'world',
+        );
+        $this->assertSame($expected, $container->getParameterBag()->all());
+    }
+
+    public function testDumpedBase64EnvParameters()
+    {
+        $container = new ContainerBuilder();
+        $container->setParameter('env(foo)', base64_encode('world'));
+        $container->setParameter('hello', '%env(base64:foo)%');
+        $container->compile();
+
+        $dumper = new PhpDumper($container);
+        $dumper->dump();
+
+        $this->assertStringEqualsFile(self::$fixturesPath.'/php/services_base64_env.php', $dumper->dump(array('class' => 'Symfony_DI_PhpDumper_Test_Base64Parameters')));
+
+        require self::$fixturesPath.'/php/services_base64_env.php';
+        $container = new \Symfony_DI_PhpDumper_Test_Base64Parameters();
+        $this->assertSame('world', $container->getParameter('hello'));
+    }
+
+    public function testCustomEnvParameters()
+    {
+        $container = new ContainerBuilder();
+        $container->setParameter('env(foo)', str_rot13('world'));
+        $container->setParameter('hello', '%env(rot13:foo)%');
+        $container->register(Rot13EnvVarProcessor::class)->addTag('container.env_var_processor');
+        $container->compile();
+
+        $dumper = new PhpDumper($container);
+        $dumper->dump();
+
+        $this->assertStringEqualsFile(self::$fixturesPath.'/php/services_rot13_env.php', $dumper->dump(array('class' => 'Symfony_DI_PhpDumper_Test_Rot13Parameters')));
+
+        require self::$fixturesPath.'/php/services_rot13_env.php';
+        $container = new \Symfony_DI_PhpDumper_Test_Rot13Parameters();
+        $this->assertSame('world', $container->getParameter('hello'));
+    }
+
+    public function testFileEnvProcessor()
+    {
+        $container = new ContainerBuilder();
+        $container->setParameter('env(foo)', __FILE__);
+        $container->setParameter('random', '%env(file:foo)%');
+        $container->compile(true);
+
+        $this->assertStringEqualsFile(__FILE__, $container->getParameter('random'));
     }
 
     /**
@@ -360,6 +430,31 @@ class PhpDumperTest extends TestCase
         $dumper->dump();
     }
 
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\ParameterCircularReferenceException
+     * @expectedExceptionMessage Circular reference detected for parameter "env(resolve:DUMMY_ENV_VAR)" ("env(resolve:DUMMY_ENV_VAR)" > "env(resolve:DUMMY_ENV_VAR)").
+     */
+    public function testCircularDynamicEnv()
+    {
+        $container = new ContainerBuilder();
+        $container->setParameter('foo', '%bar%');
+        $container->setParameter('bar', '%env(resolve:DUMMY_ENV_VAR)%');
+        $container->compile();
+
+        $dumper = new PhpDumper($container);
+        $dump = $dumper->dump(array('class' => $class = __FUNCTION__));
+
+        eval('?>'.$dump);
+        $container = new $class();
+
+        putenv('DUMMY_ENV_VAR=%foo%');
+        try {
+            $container->getParameter('bar');
+        } finally {
+            putenv('DUMMY_ENV_VAR');
+        }
+    }
+
     public function testInlinedDefinitionReferencingServiceContainer()
     {
         $container = new ContainerBuilder();
@@ -748,3 +843,16 @@ class PhpDumperTest extends TestCase
         $this->assertSame('bar', $container->getParameter('FOO'));
     }
 }
+
+class Rot13EnvVarProcessor implements EnvVarProcessorInterface
+{
+    public function getEnv($prefix, $name, \Closure $getEnv)
+    {
+        return str_rot13($getEnv($name));
+    }
+
+    public static function getProvidedTypes()
+    {
+        return array('rot13' => 'string');
+    }
+}
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/array.json b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/array.json
new file mode 100644
index 0000000000..dc27f0fa15
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/array.json
@@ -0,0 +1 @@
+[123, "abc"]
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services26.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services26.php
index 0998b23a75..3a38cff1a1 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services26.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services26.php
@@ -9,14 +9,14 @@ use Symfony\Component\DependencyInjection\Exception\RuntimeException;
 use Symfony\Component\DependencyInjection\ParameterBag\FrozenParameterBag;
 
 /**
- * ProjectServiceContainer.
+ * Symfony_DI_PhpDumper_Test_EnvParameters.
  *
  * This class has been auto-generated
  * by the Symfony Dependency Injection Component.
  *
  * @final since Symfony 3.3
  */
-class ProjectServiceContainer extends Container
+class Symfony_DI_PhpDumper_Test_EnvParameters extends Container
 {
     private $parameters;
     private $targetDirs = array();
@@ -26,6 +26,10 @@ class ProjectServiceContainer extends Container
      */
     public function __construct()
     {
+        $dir = __DIR__;
+        for ($i = 1; $i <= 5; ++$i) {
+            $this->targetDirs[$i] = $dir = dirname($dir);
+        }
         $this->parameters = $this->getDefaultParameters();
 
         $this->services = array();
@@ -71,7 +75,7 @@ class ProjectServiceContainer extends Container
     {
         $class = $this->getEnv('FOO');
 
-        return $this->services['test'] = new $class($this->getEnv('Bar'), 'foo'.$this->getEnv('FOO').'baz');
+        return $this->services['test'] = new $class($this->getEnv('Bar'), 'foo'.$this->getEnv('string:FOO').'baz', $this->getEnv('int:Baz'));
     }
 
     /**
@@ -129,6 +133,10 @@ class ProjectServiceContainer extends Container
 
     private $loadedDynamicParameters = array(
         'bar' => false,
+        'baz' => false,
+        'json' => false,
+        'db_dsn' => false,
+        'env(json_file)' => false,
     );
     private $dynamicParameters = array();
 
@@ -145,6 +153,10 @@ class ProjectServiceContainer extends Container
     {
         switch ($name) {
             case 'bar': $value = $this->getEnv('FOO'); break;
+            case 'baz': $value = $this->getEnv('int:Baz'); break;
+            case 'json': $value = $this->getEnv('json:file:json_file'); break;
+            case 'db_dsn': $value = $this->getEnv('resolve:DB'); break;
+            case 'env(json_file)': $value = ($this->targetDirs[1].'/array.json'); break;
             default: throw new InvalidArgumentException(sprintf('The dynamic parameter "%s" must be defined.', $name));
         }
         $this->loadedDynamicParameters[$name] = true;
@@ -154,6 +166,7 @@ class ProjectServiceContainer extends Container
 
     private $normalizedParameterNames = array(
         'env(foo)' => 'env(FOO)',
+        'env(db)' => 'env(DB)',
     );
 
     private function normalizeParameterName($name)
@@ -178,7 +191,9 @@ class ProjectServiceContainer extends Container
     protected function getDefaultParameters()
     {
         return array(
+            'project_dir' => '/foo/bar',
             'env(FOO)' => 'foo',
+            'env(DB)' => 'sqlite://%project_dir%/var/data.db',
         );
     }
 }
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services_base64_env.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services_base64_env.php
new file mode 100644
index 0000000000..4f4c7e79df
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services_base64_env.php
@@ -0,0 +1,167 @@
+<?php
+
+use Symfony\Component\DependencyInjection\Argument\RewindableGenerator;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\DependencyInjection\Container;
+use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
+use Symfony\Component\DependencyInjection\Exception\LogicException;
+use Symfony\Component\DependencyInjection\Exception\RuntimeException;
+use Symfony\Component\DependencyInjection\ParameterBag\FrozenParameterBag;
+
+/**
+ * Symfony_DI_PhpDumper_Test_Base64Parameters.
+ *
+ * This class has been auto-generated
+ * by the Symfony Dependency Injection Component.
+ *
+ * @final since Symfony 3.3
+ */
+class Symfony_DI_PhpDumper_Test_Base64Parameters extends Container
+{
+    private $parameters;
+    private $targetDirs = array();
+
+    /**
+     * Constructor.
+     */
+    public function __construct()
+    {
+        $this->parameters = $this->getDefaultParameters();
+
+        $this->services = array();
+
+        $this->aliases = array();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function compile()
+    {
+        throw new LogicException('You cannot compile a dumped container that was already compiled.');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isCompiled()
+    {
+        return true;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isFrozen()
+    {
+        @trigger_error(sprintf('The %s() method is deprecated since version 3.3 and will be removed in 4.0. Use the isCompiled() method instead.', __METHOD__), E_USER_DEPRECATED);
+
+        return true;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getParameter($name)
+    {
+        if (!(isset($this->parameters[$name]) || isset($this->loadedDynamicParameters[$name]) || array_key_exists($name, $this->parameters))) {
+            $name = $this->normalizeParameterName($name);
+
+            if (!(isset($this->parameters[$name]) || isset($this->loadedDynamicParameters[$name]) || array_key_exists($name, $this->parameters))) {
+                throw new InvalidArgumentException(sprintf('The parameter "%s" must be defined.', $name));
+            }
+        }
+        if (isset($this->loadedDynamicParameters[$name])) {
+            return $this->loadedDynamicParameters[$name] ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+        }
+
+        return $this->parameters[$name];
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function hasParameter($name)
+    {
+        $name = $this->normalizeParameterName($name);
+
+        return isset($this->parameters[$name]) || isset($this->loadedDynamicParameters[$name]) || array_key_exists($name, $this->parameters);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function setParameter($name, $value)
+    {
+        throw new LogicException('Impossible to call set() on a frozen ParameterBag.');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getParameterBag()
+    {
+        if (null === $this->parameterBag) {
+            $parameters = $this->parameters;
+            foreach ($this->loadedDynamicParameters as $name => $loaded) {
+                $parameters[$name] = $loaded ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+            }
+            $this->parameterBag = new FrozenParameterBag($parameters);
+        }
+
+        return $this->parameterBag;
+    }
+
+    private $loadedDynamicParameters = array(
+        'hello' => false,
+    );
+    private $dynamicParameters = array();
+
+    /**
+     * Computes a dynamic parameter.
+     *
+     * @param string The name of the dynamic parameter to load
+     *
+     * @return mixed The value of the dynamic parameter
+     *
+     * @throws InvalidArgumentException When the dynamic parameter does not exist
+     */
+    private function getDynamicParameter($name)
+    {
+        switch ($name) {
+            case 'hello': $value = $this->getEnv('base64:foo'); break;
+            default: throw new InvalidArgumentException(sprintf('The dynamic parameter "%s" must be defined.', $name));
+        }
+        $this->loadedDynamicParameters[$name] = true;
+
+        return $this->dynamicParameters[$name] = $value;
+    }
+
+    private $normalizedParameterNames = array();
+
+    private function normalizeParameterName($name)
+    {
+        if (isset($this->normalizedParameterNames[$normalizedName = strtolower($name)]) || isset($this->parameters[$normalizedName]) || array_key_exists($normalizedName, $this->parameters)) {
+            $normalizedName = isset($this->normalizedParameterNames[$normalizedName]) ? $this->normalizedParameterNames[$normalizedName] : $normalizedName;
+            if ((string) $name !== $normalizedName) {
+                @trigger_error(sprintf('Parameter names will be made case sensitive in Symfony 4.0. Using "%s" instead of "%s" is deprecated since version 3.4.', $name, $normalizedName), E_USER_DEPRECATED);
+            }
+        } else {
+            $normalizedName = $this->normalizedParameterNames[$normalizedName] = (string) $name;
+        }
+
+        return $normalizedName;
+    }
+
+    /**
+     * Gets the default parameters.
+     *
+     * @return array An array of the default parameters
+     */
+    protected function getDefaultParameters()
+    {
+        return array(
+            'env(foo)' => 'd29ybGQ=',
+        );
+    }
+}
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services_rot13_env.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services_rot13_env.php
new file mode 100644
index 0000000000..2e08cdcb42
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services_rot13_env.php
@@ -0,0 +1,196 @@
+<?php
+
+use Symfony\Component\DependencyInjection\Argument\RewindableGenerator;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\DependencyInjection\Container;
+use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
+use Symfony\Component\DependencyInjection\Exception\LogicException;
+use Symfony\Component\DependencyInjection\Exception\RuntimeException;
+use Symfony\Component\DependencyInjection\ParameterBag\FrozenParameterBag;
+
+/**
+ * Symfony_DI_PhpDumper_Test_Rot13Parameters.
+ *
+ * This class has been auto-generated
+ * by the Symfony Dependency Injection Component.
+ *
+ * @final since Symfony 3.3
+ */
+class Symfony_DI_PhpDumper_Test_Rot13Parameters extends Container
+{
+    private $parameters;
+    private $targetDirs = array();
+
+    /**
+     * Constructor.
+     */
+    public function __construct()
+    {
+        $this->parameters = $this->getDefaultParameters();
+
+        $this->services = array();
+        $this->normalizedIds = array(
+            'symfony\\component\\dependencyinjection\\tests\\dumper\\rot13envvarprocessor' => 'Symfony\\Component\\DependencyInjection\\Tests\\Dumper\\Rot13EnvVarProcessor',
+        );
+        $this->methodMap = array(
+            'Symfony\\Component\\DependencyInjection\\Tests\\Dumper\\Rot13EnvVarProcessor' => 'getRot13EnvVarProcessorService',
+            'container.env_var_processors_locator' => 'getContainer_EnvVarProcessorsLocatorService',
+        );
+
+        $this->aliases = array();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function compile()
+    {
+        throw new LogicException('You cannot compile a dumped container that was already compiled.');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isCompiled()
+    {
+        return true;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isFrozen()
+    {
+        @trigger_error(sprintf('The %s() method is deprecated since version 3.3 and will be removed in 4.0. Use the isCompiled() method instead.', __METHOD__), E_USER_DEPRECATED);
+
+        return true;
+    }
+
+    /**
+     * Gets the public 'Symfony\Component\DependencyInjection\Tests\Dumper\Rot13EnvVarProcessor' shared service.
+     *
+     * @return \Symfony\Component\DependencyInjection\Tests\Dumper\Rot13EnvVarProcessor
+     */
+    protected function getRot13EnvVarProcessorService()
+    {
+        return $this->services['Symfony\Component\DependencyInjection\Tests\Dumper\Rot13EnvVarProcessor'] = new \Symfony\Component\DependencyInjection\Tests\Dumper\Rot13EnvVarProcessor();
+    }
+
+    /**
+     * Gets the public 'container.env_var_processors_locator' shared service.
+     *
+     * @return \Symfony\Component\DependencyInjection\ServiceLocator
+     */
+    protected function getContainer_EnvVarProcessorsLocatorService()
+    {
+        return $this->services['container.env_var_processors_locator'] = new \Symfony\Component\DependencyInjection\ServiceLocator(array('rot13' => function () {
+            return ${($_ = isset($this->services['Symfony\Component\DependencyInjection\Tests\Dumper\Rot13EnvVarProcessor']) ? $this->services['Symfony\Component\DependencyInjection\Tests\Dumper\Rot13EnvVarProcessor'] : $this->services['Symfony\Component\DependencyInjection\Tests\Dumper\Rot13EnvVarProcessor'] = new \Symfony\Component\DependencyInjection\Tests\Dumper\Rot13EnvVarProcessor()) && false ?: '_'};
+        }));
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getParameter($name)
+    {
+        if (!(isset($this->parameters[$name]) || isset($this->loadedDynamicParameters[$name]) || array_key_exists($name, $this->parameters))) {
+            $name = $this->normalizeParameterName($name);
+
+            if (!(isset($this->parameters[$name]) || isset($this->loadedDynamicParameters[$name]) || array_key_exists($name, $this->parameters))) {
+                throw new InvalidArgumentException(sprintf('The parameter "%s" must be defined.', $name));
+            }
+        }
+        if (isset($this->loadedDynamicParameters[$name])) {
+            return $this->loadedDynamicParameters[$name] ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+        }
+
+        return $this->parameters[$name];
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function hasParameter($name)
+    {
+        $name = $this->normalizeParameterName($name);
+
+        return isset($this->parameters[$name]) || isset($this->loadedDynamicParameters[$name]) || array_key_exists($name, $this->parameters);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function setParameter($name, $value)
+    {
+        throw new LogicException('Impossible to call set() on a frozen ParameterBag.');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getParameterBag()
+    {
+        if (null === $this->parameterBag) {
+            $parameters = $this->parameters;
+            foreach ($this->loadedDynamicParameters as $name => $loaded) {
+                $parameters[$name] = $loaded ? $this->dynamicParameters[$name] : $this->getDynamicParameter($name);
+            }
+            $this->parameterBag = new FrozenParameterBag($parameters);
+        }
+
+        return $this->parameterBag;
+    }
+
+    private $loadedDynamicParameters = array(
+        'hello' => false,
+    );
+    private $dynamicParameters = array();
+
+    /**
+     * Computes a dynamic parameter.
+     *
+     * @param string The name of the dynamic parameter to load
+     *
+     * @return mixed The value of the dynamic parameter
+     *
+     * @throws InvalidArgumentException When the dynamic parameter does not exist
+     */
+    private function getDynamicParameter($name)
+    {
+        switch ($name) {
+            case 'hello': $value = $this->getEnv('rot13:foo'); break;
+            default: throw new InvalidArgumentException(sprintf('The dynamic parameter "%s" must be defined.', $name));
+        }
+        $this->loadedDynamicParameters[$name] = true;
+
+        return $this->dynamicParameters[$name] = $value;
+    }
+
+    private $normalizedParameterNames = array();
+
+    private function normalizeParameterName($name)
+    {
+        if (isset($this->normalizedParameterNames[$normalizedName = strtolower($name)]) || isset($this->parameters[$normalizedName]) || array_key_exists($normalizedName, $this->parameters)) {
+            $normalizedName = isset($this->normalizedParameterNames[$normalizedName]) ? $this->normalizedParameterNames[$normalizedName] : $normalizedName;
+            if ((string) $name !== $normalizedName) {
+                @trigger_error(sprintf('Parameter names will be made case sensitive in Symfony 4.0. Using "%s" instead of "%s" is deprecated since version 3.4.', $name, $normalizedName), E_USER_DEPRECATED);
+            }
+        } else {
+            $normalizedName = $this->normalizedParameterNames[$normalizedName] = (string) $name;
+        }
+
+        return $normalizedName;
+    }
+
+    /**
+     * Gets the default parameters.
+     *
+     * @return array An array of the default parameters
+     */
+    protected function getDefaultParameters()
+    {
+        return array(
+            'env(foo)' => 'jbeyq',
+        );
+    }
+}
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services26.yml b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services26.yml
index 2ef23c1af5..d573e810db 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services26.yml
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/services26.yml
@@ -1,6 +1,11 @@
 parameters:
+    project_dir: '/foo/bar'
     env(FOO): foo
+    env(DB): 'sqlite://%%project_dir%%/var/data.db'
     bar: '%env(FOO)%'
+    baz: '%env(int:Baz)%'
+    json: '%env(json:file:json_file)%'
+    db_dsn: '%env(resolve:DB)%'
 
 services:
     test:
@@ -8,3 +13,4 @@ services:
         arguments:
             - '%env(Bar)%'
             - 'foo%bar%baz'
+            - '%baz%'