My PHP application requires register_globals be on\off. How can I do this?

Depending on the PHP version you are using and the hosting package you are on Register Globals might be on or off.  To change it you generally need to add the following line to a .htaccess file in your domain's webroot folder (if there is no .htaccess file there then just create one):

php_value "register_globals" "1"
OR
php_value "register_globals" "0"

The first is to enable register_globals while the second command disables it.

If you are using PHP in cgi-mode however (only on cp.blacknight.com) this will not work.  You will need to use the ini_set() function:
http://ie2.php.net/ini_set

Please note that .htaccess files are Linux-specific and won't work on windows hosting packages.