Doug,
PHP session support is enabled by default on our web hosting cluster. If you'd like a detailed breakdown of what is currently enabled, please refer to the following page:
http://sonic.net/support/web_resources/phpinfo/53.php
Please note that by default, PHP4 is used - if you'd like to enable PHP 5.3 (the newest version we have available), follow the instructions on our support page:
https://wiki.sonic.net/wiki/Php5
-- Joe