Changing the header image using WPML

You can use site_url() or get_site_url(). Depending on your install and setup, you could as well use network_site_url() – which is what I would prefer as it falls back to site_url() internally if it is no multisite setup.

The site_url( $path, $scheme ); function also takes two arguments:

1. The $path can be used to append a path to the URl in case you need to point somewhere custom.
2. Omit the second one, as it’s the scheme (http/s) and will be set automatically – only use it if you want to force a scheme.

Note: You might want to make your switch a bit more fail save:

switch ( $foo )
{
    case 'bar' :
        return 'I am bar';
        break;

    case default :
    case 'baz' :
        return 'I am baz';
        break;
}

Having a default will save you from failing when none of the conditions are met – with language you might want to use American English. Also you can return immediately as there is nothing which shall happen with the switch result afterwards.