Set Laravel User Locale in Middleware

To set the global Laravel language (locale), you need to use the app()->setLocale() method. But the question is: where to put this method if you want to set the locale based on a DB field like users.language?

Such global settings are often put in the AppServiceProvider, but in this case, it wouldn't work, because you don't have access to Auth:::user() there, you would get an error "Attempt to read property on null":

The reason is that at the time of loading the AppServiceProvider, the session isn't initialized yet, and the User object doesn't exist.

That's why we need to use Middleware.

php artisan make:middleware SetLocale

Then, in the Middleware, you can set the locale from the $request->user() or auth()->user():

app/Http/Middleware/SetLocale.php

class SetLocale
{
    public function handle($request, Closure $next)
    {
        if(! $request->user()) {
            return $next($request);
        }
 
        $language = $request->user()->language;
 
        if (isset($language)) {
            app()->setLocale($language);
        }
 
        return $next($request);
    }
}

And then you have 2 options to use that Middleware.

Option 1: Adding Middleware to Global Middleware Stack

bootstrap/app.php:

return Application::configure(basePath: dirname(__DIR__))
    ->withRouting(
        web: __DIR__.'/../routes/web.php',
        commands: __DIR__.'/../routes/console.php',
        health: '/up',
    )
    ->withMiddleware(function (Middleware $middleware) {
        $middleware->web([ 
            \App\Http\Middleware\SetLocale::class,
        ]);
    })
    ->withExceptions(function (Exceptions $exceptions) {
        //
    })->create();

This way, the locale will be set for all routes which are in the web middleware group, which means all routes in the routes/web.php file.

Option 2: Adding Middleware to Specific Route(s)

bootstrap/app.php

return Application::configure(basePath: dirname(__DIR__))
    ->withRouting(
        web: __DIR__.'/../routes/web.php',
        commands: __DIR__.'/../routes/console.php',
        health: '/up',
    )
    ->withMiddleware(function (Middleware $middleware) {
        $middleware->alias([ 
            'setLocale' => \App\Http\Middleware\SetLocale::class,
        ]);
    })
    ->withExceptions(function (Exceptions $exceptions) {
        //
    })->create();

And then in your routes file add it to the routes or route groups:

Route::group(['middleware' => ['auth', 'setLocale']], function () {
    // ...
});

This way, only specific routes will have the locale set.