Laravel / Locale (middleware)

Kernel.php

<?php // app/Http/kernel.php

namespace App\Http;

use Illuminate\Foundation\Http\Kernel as HttpKernel;

class Kernel extends HttpKernel
{
    //...
    protected $middlewareGroups = [
        'web' => [
            // ...
            \Illuminate\Session\Middleware\StartSession::class,
            \App\Http\Middleware\Locale::class, // <-- THE LOCALE MIDDLEWARE IS AFTER 'START-SESSION' 
            // ...
        ]
    ];
    //...
}

languages.php

<?php // config/languages.php

return [
    'en' => 'English',
    'pt' => 'Portuguese',
];

Locale.php

<?php // app/Http/Middleware/Locale.php

namespace App\Http\Middleware;

use Closure;
use Session;
use Config;
use App;

class Locale
{
    public function handle($request, Closure $next)
    {
        $language = Session::get('language', Config::get('app.locale'));
        $language = array_key_exists($language, Config::get('languages')) ? $language : Config::get('app.fallback_locale');
        App::setLocale($language);

        return $next($request);
    }
}

site.blade.php

<?php // resources/views/layouts/site.php

<form id='locale-form' method='post' action="{{ route('site.language')}}">
    {{ csrf_field() }}
    <input type='hidden' id='language_field' name='locale' value='{{ App::getLocale() }}'/>
</form>
            
<button id='pt' type='button'>PT</button>
<button id='en' type='button'>EN</button>

<script>
document.addEventListener("DOMContentLoaded", function () 
{
    $pt = document.querySelector('button#pt');
    $en = document.querySelector('button#en');

    $pt.addEventListener('click', function (e) {
        document.querySelector('#locale-form #language_field').value = 'pt'
        document.querySelector('#locale-form').submit();
    })

    $en.addEventListener('click', function (e) {
        document.querySelector('#locale-form #language_field').value = 'en'
        document.querySelector('#locale-form').submit();
    })
})
</script>

SiteController.php

<?php // app/Http/Controllers/SiteController.php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class SiteController extends Controller
{
    public function language(Request $request)
    {
        \Session::put('language', $request->get('locale', 'en'));
        \App::setLocale($request->get('locale', 'pt'));
        return \Redirect::back();
    }
}

web.php

<?php // routes/web.php

Route::post('/language', 'SiteController@language')->name('site.language');