To handle this at the Laravel level you can use middleware. Middleware provides a convenient mechanism to inspect and filter HTTP requests entering your application.

Here are examples of how you can do this.

First, create a new middleware by running the following command:

php artisan make:middleware SubdomainRedirectMiddleware

Next, open the newly created file app/Http/Middleware/SubdomainRedirectMiddleware.php and add the redirection logic to the handle method:

public function handle(Request $request, Closure $next)
{
    // Replace 'mydomain' with your actual domain
    if ($request->getHost() === 'mydomain.com') {

        // Replace 'subdomain' with your actual subdomain
        return redirect()->to(str_replace('mydomain.com', 'subdomain.mydomain.com', $request->fullUrl()));
    }

    return $next($request);
}

Then, you need to register this middleware. Open app/Http/Kernel.php and add the following lines to the routeMiddleware array:

protected $routeMiddleware = [
    'subdomain.redirect' => \App\Http\Middleware\SubdomainRedirectMiddleware::class,
];

Route::group(['middleware' => 'subdomain.redirect'], function () {
    // All your routes go here
});

Please replace 'mydomain' and 'subdomain' with your actual domain and subdomain in SubdomainRedirectMiddleware.php.

▽This is a reference https://www.w3schools.in/laravel/middleware