install symfony demo with installer

app/tests/bootstrap.php

@@ -0,0 +1,20 @@
+<?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.
+ */
+
+use Symfony\Component\Dotenv\Dotenv;
+
+require dirname(__DIR__).'/vendor/autoload.php';
+
+if (file_exists(dirname(__DIR__).'/config/bootstrap.php')) {
+    require dirname(__DIR__).'/config/bootstrap.php';
+} elseif (method_exists(Dotenv::class, 'bootEnv')) {
+    (new Dotenv())->bootEnv(dirname(__DIR__).'/.env');
+}