diff --git a/bin/composer b/bin/composer
index ca6ecc6b5..385508e75 100755
--- a/bin/composer
+++ b/bin/composer
@@ -10,6 +10,7 @@ require __DIR__.'/../src/bootstrap.php';
 
 use Composer\Console\Application;
 use Composer\XdebugHandler\XdebugHandler;
+use Composer\Util\Platform;
 
 error_reporting(-1);
 
@@ -57,8 +58,7 @@ if (function_exists('ini_set')) {
     unset($memoryLimit);
 }
 
-$_SERVER['COMPOSER_BINARY'] = realpath($_SERVER['argv'][0]);
-putenv('COMPOSER_BINARY='.$_SERVER['COMPOSER_BINARY']);
+Platform::setEnv('COMPOSER_BINARY', realpath($_SERVER['argv'][0]));
 
 // run the command application
 $application = new Application();
diff --git a/src/Composer/Autoload/AutoloadGenerator.php b/src/Composer/Autoload/AutoloadGenerator.php
index 8d7bd73a4..474efcbd5 100644
--- a/src/Composer/Autoload/AutoloadGenerator.php
+++ b/src/Composer/Autoload/AutoloadGenerator.php
@@ -24,6 +24,7 @@ use Composer\Repository\PlatformRepository;
 use Composer\Semver\Constraint\Bound;
 use Composer\Semver\Constraint\MatchAllConstraint;
 use Composer\Util\Filesystem;
+use Composer\Util\Platform;
 use Composer\Script\ScriptEvents;
 use Composer\Util\PackageSorter;
 use Composer\Json\JsonFile;
@@ -158,8 +159,7 @@ class AutoloadGenerator
 
             // set COMPOSER_DEV_MODE in case not set yet so it is available in the dump-autoload autoload
             if (!isset($_SERVER['COMPOSER_DEV_MODE'])) {
-                $_SERVER['COMPOSER_DEV_MODE'] = $this->devMode ? '1' : '0';
-                putenv('COMPOSER_DEV_MODE='.$_SERVER['COMPOSER_DEV_MODE']);
+                Platform::putEnv('COMPOSER_DEV_MODE', $this->devMode ? '1' : '0');
             }
 
             $this->eventDispatcher->dispatchScript(ScriptEvents::PRE_AUTOLOAD_DUMP, $this->devMode, array(), array(
diff --git a/src/Composer/Command/CreateProjectCommand.php b/src/Composer/Command/CreateProjectCommand.php
index 4734f9cab..9bdd33ae3 100644
--- a/src/Composer/Command/CreateProjectCommand.php
+++ b/src/Composer/Command/CreateProjectCommand.php
@@ -37,6 +37,7 @@ use Symfony\Component\Finder\Finder;
 use Composer\Json\JsonFile;
 use Composer\Config\JsonConfigSource;
 use Composer\Util\Filesystem;
+use Composer\Util\Platform;
 use Composer\Util\ProcessExecutor;
 use Composer\Package\Version\VersionParser;
 
@@ -453,8 +454,7 @@ EOT
         $io->writeError('<info>Created project in ' . $directory . '</info>');
         chdir($directory);
 
-        $_SERVER['COMPOSER_ROOT_VERSION'] = $package->getPrettyVersion();
-        putenv('COMPOSER_ROOT_VERSION='.$_SERVER['COMPOSER_ROOT_VERSION']);
+        Platform::putEnv('COMPOSER_ROOT_VERSION', $package->getPrettyVersion());
 
         return $installedFromVcs;
     }
diff --git a/src/Composer/Command/GlobalCommand.php b/src/Composer/Command/GlobalCommand.php
index 96a6b5f5e..c78ea7109 100644
--- a/src/Composer/Command/GlobalCommand.php
+++ b/src/Composer/Command/GlobalCommand.php
@@ -14,6 +14,7 @@ namespace Composer\Command;
 
 use Composer\Factory;
 use Composer\Util\Filesystem;
+use Composer\Util\Platform;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Input\InputArgument;
 use Symfony\Component\Console\Input\StringInput;
@@ -81,8 +82,7 @@ EOT
 
         // The COMPOSER env var should not apply to the global execution scope
         if (getenv('COMPOSER')) {
-            putenv('COMPOSER');
-            unset($_SERVER['COMPOSER']);
+            Platform::clearEnv('COMPOSER');
         }
 
         // change to global dir
diff --git a/src/Composer/Command/RunScriptCommand.php b/src/Composer/Command/RunScriptCommand.php
index c45507b1f..1ecf1e0c1 100644
--- a/src/Composer/Command/RunScriptCommand.php
+++ b/src/Composer/Command/RunScriptCommand.php
@@ -15,6 +15,7 @@ namespace Composer\Command;
 use Composer\Script\Event as ScriptEvent;
 use Composer\Script\ScriptEvents;
 use Composer\Util\ProcessExecutor;
+use Composer\Util\Platform;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Input\InputArgument;
@@ -103,8 +104,7 @@ EOT
             ProcessExecutor::setTimeout((int) $timeout);
         }
 
-        $_SERVER['COMPOSER_DEV_MODE'] = $devMode ? '1' : '0';
-        putenv('COMPOSER_DEV_MODE='.$_SERVER['COMPOSER_DEV_MODE']);
+        Platform::putEnv('COMPOSER_DEV_MODE', $devMode ? '1' : '0');
 
         return $composer->getEventDispatcher()->dispatchScript($script, $devMode, $args);
     }
diff --git a/src/Composer/Console/Application.php b/src/Composer/Console/Application.php
index bdb8700aa..177f7220a 100644
--- a/src/Composer/Console/Application.php
+++ b/src/Composer/Console/Application.php
@@ -143,8 +143,7 @@ class Application extends BaseApplication
 
         if ($input->hasParameterOption('--no-cache')) {
             $io->writeError('Disabling cache usage', true, IOInterface::DEBUG);
-            $_SERVER['COMPOSER_CACHE_DIR'] = Platform::isWindows() ? 'nul' : '/dev/null';
-            putenv('COMPOSER_CACHE_DIR='.$_SERVER['COMPOSER_CACHE_DIR']);
+            Platform::putEnv('COMPOSER_CACHE_DIR', Platform::isWindows() ? 'nul' : '/dev/null');
         }
 
         // switch working dir
diff --git a/src/Composer/EventDispatcher/EventDispatcher.php b/src/Composer/EventDispatcher/EventDispatcher.php
index a18112c4b..5a06314d8 100644
--- a/src/Composer/EventDispatcher/EventDispatcher.php
+++ b/src/Composer/EventDispatcher/EventDispatcher.php
@@ -247,9 +247,12 @@ class EventDispatcher
                     }
 
                     if (strpos($exec, '@putenv ') === 0) {
-                        putenv(substr($exec, 8));
-                        list($var, $value) = explode('=', substr($exec, 8), 2);
-                        $_SERVER[$var] = $value;
+                        if (false === strpos($exec, '=')) {
+                            Platform::clearEnv(substr($exec, 8));
+                        } else {
+                            list($var, $value) = explode('=', substr($exec, 8), 2);
+                            Platform::putEnv($var, $value);
+                        }
 
                         continue;
                     }
@@ -274,8 +277,7 @@ class EventDispatcher
                         $finder = new PhpExecutableFinder();
                         $phpPath = $finder->find(false);
                         if ($phpPath) {
-                            $_SERVER['PHP_BINARY'] = $phpPath;
-                            putenv('PHP_BINARY=' . $_SERVER['PHP_BINARY']);
+                            Platform::putEnv('PHP_BINARY', $phpPath);
                         }
 
                         if (Platform::isWindows()) {
@@ -539,8 +541,7 @@ class EventDispatcher
         if (is_dir($binDir)) {
             $binDir = realpath($binDir);
             if (isset($_SERVER[$pathStr]) && !preg_match('{(^|'.PATH_SEPARATOR.')'.preg_quote($binDir).'($|'.PATH_SEPARATOR.')}', $_SERVER[$pathStr])) {
-                $_SERVER[$pathStr] = $binDir.PATH_SEPARATOR.getenv($pathStr);
-                putenv($pathStr.'='.$_SERVER[$pathStr]);
+                Platform::putEnv($pathStr, $binDir.PATH_SEPARATOR.getenv($pathStr));
             }
         }
     }
diff --git a/src/Composer/Installer.php b/src/Composer/Installer.php
index 8e2a49367..c803edfdf 100644
--- a/src/Composer/Installer.php
+++ b/src/Composer/Installer.php
@@ -56,6 +56,7 @@ use Composer\Repository\RepositoryInterface;
 use Composer\Repository\RepositoryManager;
 use Composer\Repository\LockArrayRepository;
 use Composer\Script\ScriptEvents;
+use Composer\Util\Platform;
 
 /**
  * @author Jordi Boggiano <j.boggiano@seld.be>
@@ -224,8 +225,7 @@ class Installer
         }
 
         if ($this->runScripts) {
-            $_SERVER['COMPOSER_DEV_MODE'] = $this->devMode ? '1' : '0';
-            putenv('COMPOSER_DEV_MODE='.$_SERVER['COMPOSER_DEV_MODE']);
+            Platform::putEnv('COMPOSER_DEV_MODE', $this->devMode ? '1' : '0');
 
             // dispatch pre event
             // should we treat this more strictly as running an update and then running an install, triggering events multiple times?
diff --git a/src/Composer/Util/Git.php b/src/Composer/Util/Git.php
index 3290c6d85..67d42b7c2 100644
--- a/src/Composer/Util/Git.php
+++ b/src/Composer/Util/Git.php
@@ -353,29 +353,24 @@ class Git
 
         // added in git 1.7.1, prevents prompting the user for username/password
         if (getenv('GIT_ASKPASS') !== 'echo') {
-            putenv('GIT_ASKPASS=echo');
-            $_SERVER['GIT_ASKPASS'] = 'echo';
+            Platform::putEnv('GIT_ASKPASS', 'echo');
         }
 
         // clean up rogue git env vars in case this is running in a git hook
         if (getenv('GIT_DIR')) {
-            putenv('GIT_DIR');
-            unset($_SERVER['GIT_DIR']);
+            Platform::clearEnv('GIT_DIR');
         }
         if (getenv('GIT_WORK_TREE')) {
-            putenv('GIT_WORK_TREE');
-            unset($_SERVER['GIT_WORK_TREE']);
+            Platform::clearEnv('GIT_WORK_TREE');
         }
 
         // Run processes with predictable LANGUAGE
         if (getenv('LANGUAGE') !== 'C') {
-            putenv('LANGUAGE=C');
-            $_SERVER['LANGUAGE'] = 'C';
+            Platform::putEnv('LANGUAGE', 'C');
         }
 
         // clean up env for OSX, see https://github.com/composer/composer/issues/2146#issuecomment-35478940
-        putenv("DYLD_LIBRARY_PATH");
-        unset($_SERVER['DYLD_LIBRARY_PATH']);
+        Platform::clearEnv('DYLD_LIBRARY_PATH');
     }
 
     public static function getGitHubDomainsRegex(Config $config)
diff --git a/src/Composer/Util/Platform.php b/src/Composer/Util/Platform.php
index 5693247c8..deca14db2 100644
--- a/src/Composer/Util/Platform.php
+++ b/src/Composer/Util/Platform.php
@@ -24,6 +24,33 @@ class Platform
     /** @var ?bool */
     private static $isWindowsSubsystemForLinux = null;
 
+    /**
+     * putenv() equivalent but updates the runtime global variables too
+     *
+     * @param  string $name
+     * @param  string $value
+     * @return void
+     */
+    public function putEnv($name, $value)
+    {
+        $value = (string) $value;
+        putenv($name . '=' . $value);
+        $_SERVER[$name] = $_ENV[$name] = $value;
+    }
+
+    /**
+     * putenv('X') equivalent but updates the runtime global variables too
+     *
+     * @param  string $name
+     * @param  string $value
+     * @return void
+     */
+    public function clearEnv($name)
+    {
+        putenv($name);
+        unset($_SERVER[$name], $_ENV[$name]);
+    }
+
     /**
      * Parses tildes and environment variables in paths.
      *
diff --git a/src/Composer/Util/Svn.php b/src/Composer/Util/Svn.php
index da934c161..2f7d070ab 100644
--- a/src/Composer/Util/Svn.php
+++ b/src/Composer/Util/Svn.php
@@ -85,8 +85,7 @@ class Svn
     public static function cleanEnv()
     {
         // clean up env for OSX, see https://github.com/composer/composer/issues/2146#issuecomment-35478940
-        putenv("DYLD_LIBRARY_PATH");
-        unset($_SERVER['DYLD_LIBRARY_PATH']);
+        Platform::clearEnv('DYLD_LIBRARY_PATH');
     }
 
     /**
diff --git a/tests/Composer/Test/ApplicationTest.php b/tests/Composer/Test/ApplicationTest.php
index 31fdcd1ec..f3fb28ab2 100644
--- a/tests/Composer/Test/ApplicationTest.php
+++ b/tests/Composer/Test/ApplicationTest.php
@@ -18,6 +18,13 @@ use Symfony\Component\Console\Output\OutputInterface;
 
 class ApplicationTest extends TestCase
 {
+    public function tearDown()
+    {
+        parent::tearDown();
+
+        putenv('COMPOSER_NO_INTERACTION');
+    }
+
     public function testDevWarning()
     {
         $application = new Application;