install symfony demo with installer

app/src/Twig/AppExtension.php

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+<?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 App\Twig;
+
+use Symfony\Component\Intl\Locales;
+use Twig\Extension\AbstractExtension;
+use Twig\TwigFunction;
+
+/**
+ * See https://symfony.com/doc/current/templating/twig_extension.html.
+ *
+ * @author Ryan Weaver <weaverryan@gmail.com>
+ * @author Javier Eguiluz <javier.eguiluz@gmail.com>
+ * @author Julien ITARD <julienitard@gmail.com>
+ */
+class AppExtension extends AbstractExtension
+{
+    private $localeCodes;
+    private $locales;
+
+    public function __construct(string $locales)
+    {
+        $localeCodes = explode('|', $locales);
+        sort($localeCodes);
+        $this->localeCodes = $localeCodes;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getFunctions(): array
+    {
+        return [
+            new TwigFunction('locales', [$this, 'getLocales']),
+        ];
+    }
+
+    /**
+     * Takes the list of codes of the locales (languages) enabled in the
+     * application and returns an array with the name of each locale written
+     * in its own language (e.g. English, Français, Español, etc.).
+     */
+    public function getLocales(): array
+    {
+        if (null !== $this->locales) {
+            return $this->locales;
+        }
+
+        $this->locales = [];
+        foreach ($this->localeCodes as $localeCode) {
+            $this->locales[] = ['code' => $localeCode, 'name' => Locales::getName($localeCode, $localeCode)];
+        }
+
+        return $this->locales;
+    }
+}