Dynamically changing supported languages

I tried to play a bit with the code of the page you suggested, but I couldn't find a solution, maybe it's a bit too much for my abilities.

I didn't test it, but I think all you have to do is define a new library in your app that extends the core class:

PHP Code:

<?php
namespace App\Libraries;

use CodeIgniter\HTTP\IncomingRequest as BaseIncomingRequest;

class IncomingRequest extends BaseIncomingRequest
{
    public function __construct($config, ?URI $uri = null, $body = 'php://input', ?UserAgent $userAgent = null)
    {
        parent::__construct($config, $uri, $body, $userAgent);
        // your code here
        $this->validLocales = service('settings')->get('App.supportedLocales'); 
    }
} 


Then add a request() service in app/Config/Services.php that will load your library. You can copy the one in System/Config/Services.php and add a "use" statement to use your library:

PHP Code:

use App\Libraries\IncomingRequest;

    /**
    * The Request class models an HTTP request.
    *
    * @return IncomingRequest
    */
    public static function request(?App $config = null, bool $getShared = true)
    {
        if ($getShared) {
            return static::getSharedInstance('request', $config);
        }

        $config = $config ?? config('App');

        return new IncomingRequest(
            $config,
            AppServices::uri(),
            'php://input',
            new UserAgent()
        );
    } 


Like I said, I didn't test this code, but it should be close to what you need to do.