Is valid this base_url setup??

I use the following snippet code

PHP Code:

$allowed_domains = array('site1.com', 'site2.com');
$default_domain  = 'site1.com';

if (in_array($_SERVER['HTTP_HOST'], $allowed_domains, TRUE))
{
    $domain = $_SERVER['HTTP_HOST'];
}
else
{
    $domain = $default_domain;
}

if ( ! empty($_SERVER['HTTPS']))
{
    $config['base_url'] = 'https://'.$domain;
}
else
{
    $config['base_url'] = 'http://'.$domain;
}