How to change the ENVIRONMENT type

Code:

if(! defined('ENVIRONMENT') )
{
    $domain = strtolower($_SERVER['HTTP_HOST']);
    switch($domain)
    {
        case 'www.yoursite.com' :
            define('ENVIRONMENT', 'production');
        break;
        case 'test.yoursite.com' :
            define('ENVIRONMENT', 'testing');
        break;
        default :
            define('ENVIRONMENT', 'development');
        break;
    }
}

I'm using the above code for my application. Hope it helps