add detection for Accept-Language

app/Http/Middleware/Internationalization.php

@@ -16,9 +16,11 @@ class Internationalization
             session(['locale' => Cookie::get('locale')]);
         }
 
-        if (Session::has('locale') && Arr::exists(config('locales'), session('locale'))) {
+        if (Session::has('locale')) {
             // Set app locale dynamically
             App::setLocale(session('locale'));
+        } else {
+            App::setLocale($request->getPreferredLanguage());
         }
 
         return $next($request);

config/app.php

@@ -74,7 +74,7 @@ return [
     |
     */
 
-    'locale' => 'zh-CN',
+    'locale' => 'zh_CN',
 
     /*
     |--------------------------------------------------------------------------

config/locales.php

@@ -9,6 +9,6 @@ return [
     | Available Languages
     |
     */
-    'zh-CN' => '简体中文',
+    'zh_CN' => '简体中文',
     'en'    => 'English'
 ];