How to set language for user register page / form per subdomain

Question

For a custom module, I need to change the language of the registration form based on the subdomain the user is currently active on.

I tried changing the global $language variable in hook_form_user_register_form_alter, but that does not work ($language variable is also not set at that point). I also tried setting the language in the $user object, but also no dice (probably because it is an anonymous user).

Finally I took a look at the language negotiation api, but setting up negotiation providers seems overkill for this (and haven't it studied enough to get a grasp on how to use it).

I just need to render the registration page in a different (but already available) language on /user/register, based on the subdomain. What would be the best way to achieve this.

I'm using Drupal 7.

Answer 1

Maybe you can use the Domain Locale module. It allows you to change the available and default languages per domain.

Answer 2

I may not be understanding the question, but if you go here:

/admin/config/regional/language/configure

You can set how languages are set (Determine the language from the URL (Path prefix or domain).

Domains can be configured here: /admin/config/regional/language/edit/

Answer 3

Based on how it's done in the Domain Locale module (thanks Matt for pointing it out), I am now using this in hook_init:

if (strpos($cp, 'user/register') === 0 || strpos($cp, 'user/password') === 0 || strpos($cp, 'user/reset') === 0) {
    global $language;
    $lang = my_get_language_function();
    $languages = language_list();
    if (!empty($lang) && isset($languages[$lang]))
        $language = $languages[$lang];
    return;
}