Allow to override .env files per env

symfony/framework-bundle/4.2/src/Kernel.php

@@ -5,7 +5,9 @@ namespace App;
 use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
 use Symfony\Component\Config\Loader\LoaderInterface;
 use Symfony\Component\Config\Resource\FileResource;
+use Symfony\Component\Console\Application;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\Dotenv\Dotenv;
 use Symfony\Component\HttpKernel\Kernel as BaseKernel;
 use Symfony\Component\Routing\RouteCollectionBuilder;
 
@@ -58,4 +60,29 @@ class Kernel extends BaseKernel
         $routes->import($confDir.'/{routes}/'.$this->environment.'/**/*'.self::CONFIG_EXTS, '/', 'glob');
         $routes->import($confDir.'/{routes}'.self::CONFIG_EXTS, '/', 'glob');
     }
+
+    public static function bootstrapCli(array &$argv)
+    {
+        // consume --env and --no-debug from the command line
+        Application::bootstrapEnv($argv);
+    }
+
+    public static function bootstrapEnv(string $env = null)
+    {
+        if (null !== $env) {
+            putenv('APP_ENV='.$_SERVER['APP_ENV'] = $env);
+        }
+
+        if ('prod' !== $_SERVER['APP_ENV'] = $_SERVER['APP_ENV'] ?? $_ENV['APP_ENV'] ?? null) {
+            if (!class_exists(Dotenv::class)) {
+                throw new \RuntimeException('The "APP_ENV" environment variable is not defined. You need to set it or run "composer require symfony/dotenv" to load it from a ".env" file.');
+            }
+
+            (new Dotenv())->loadEnv(\dirname(__DIR__).'/.env');
+        }
+
+        $_SERVER['APP_ENV'] = $_ENV['APP_ENV'] = $_SERVER['APP_ENV'] ?? $_SERVER['APP_ENV'] ?? 'dev';
+        $_SERVER['APP_DEBUG'] = $_SERVER['APP_DEBUG'] ?? $_ENV['APP_DEBUG'] ?? 'prod' !== $_SERVER['APP_ENV'];
+        $_SERVER['APP_DEBUG'] = $_ENV['APP_DEBUG'] = (int) $_SERVER['APP_DEBUG'] || filter_var($_SERVER['APP_DEBUG'], FILTER_VALIDATE_BOOLEAN) ? '1' : '0';
+    }
 }