Our new servers run PHP version 5.3. We also have servers running PHP version 5.2. New customers are put on a PHP 5.3 server automatically unless they specifically request a PHP 5.2 server during the hosting order process.
We keep all versions of PHP up to date with the latest updates from their respective branches. Once your hosting account has been created, you can view your PHP configuration in the control panel in the Development Tools -> PHP section.