Pantheon settings.php URL normalizing code - rewrites www.sitename.com to sitename.com

settings.php redirect for Pantheon sites

if (isset($_SERVER['PANTHEON_ENVIRONMENT']) && 
  $_SERVER['PANTHEON_ENVIRONMENT'] === 'live') {
  if (  $_SERVER['HTTP_HOST'] == 'live.SITENAME.gotpantheon.com' ||
      $_SERVER['HTTP_HOST'] == 'www.SITENAME.com') {
    header('HTTP/1.0 301 Moved Permanently'); 
    header('Location: http://SITENAME.com'. $_SERVER['REQUEST_URI']); 
    exit();
  }
}