laravel multi-language switch and change locale on load

Question

I've implemented the language switch functionality following this post and it works perfectly but just when you click on the language switch, though I would like to change the locale and store it in the App when the page is loaded.

My function it's a bit different from the one in the post, I've added an else if just to make sure that the locale it's in the accepted languages

App/Middleware/Localization.php

public function handle($request, Closure $next)
{
    $availableLangs  = array('en', 'hu', 'pt', 'ro', 'sv');
    $userLangs = substr($request->server('HTTP_ACCEPT_LANGUAGE'), 0, 2);

    if (\Session::has('locale'))
    {
        \App::setlocale(\Session::get('locale'));
    }
    else if (in_array($userLangs, $availableLangs))
    {
        \App::setLocale($userLangs);
      // Session::push('locale', $userLangs);
    }
    return $next($request);
}

How can I reuse this function or create a new function to achieve the same result but when you load the website?

I have a lot of route so I think that I will need a function in order to don't repeat the same code over and over.

I don't use the locale on the URL and I don't want to use it, so please don't propose a solution that includes that option.

Example of my URLS (each URL can be view with all the available languages)

domain/city1/
domain/city1/dashboard/
domain/city2/
domain/city2/dashboard/
domain/admin/

I don't want:

domain/city1/en/...
domain/city1/pt/...

Answer 1

Probably you need something like this, whenever the page load initially there won't be any server value so it cannot set value for the $userLangs variable. So as per your code, the if statement fails since there is no session value and the elseif condition also fails since there is no value set for $userLangs which cannot be found in the $availableLangs. Just add one else condition to set a default lanuage of the website when there is no prefered user language.

public function handle($request, Closure $next) 
{
    $availableLangs  = array('en', 'hu', 'pt', 'ro', 'sv');
    $userLangs = substr($request->server('HTTP_ACCEPT_LANGUAGE'), 0, 2);

    if (\Session::has('locale'))
    {
        \App::setlocale(\Session::get('locale'));
    }
    else if (in_array($userLangs, $availableLangs))
    {
        \App::setLocale($userLangs);
        Session::put('locale', $userLangs);
    }
    else {
        \App::setLocale('en');
        Session::put('locale', 'en');
    }
    return $next($request);
}