oscommerce https admin php configuration

[kelvin95]

How do you make the oscommerce admin login and admin content to be under https:?
I have tried to change it from configure.php files in this way
<?php
  define('HTTP_SERVER', 'https://servername.com);
  define('HTTPS_SERVER', 'https:// servername.com ');
  define('ENABLE_SSL', 'true');
  define('HTTP_CATALOG_SERVER', 'https:// servername.com ');
  define('HTTPS_CATALOG_SERVER', 'https:// servername.com ');
  define('ENABLE_SSL_CATALOG', 'true');

But it is giving me the "redirected you too many times." error.

Could you advise me on what would cause this and  suggest any solutions?