admin/environment/custom check/php check register globals
I'm no expert on this, but rather than leave it empty:
If register_globals is ON there are certain security risks so it should be turned off.
You can check the setting under the administration interface for server for your site.
Moodle will often give a very short description about how to change this if it is set to ON.
Here is an example from a hosted site:
I found a forum post on the Siteground site about this problem. They said that if one had php 5.1 that register_globals was ON by default and that under 5.1 a php.ini could NOT effect it. But that one can easily change the used php version with a suitable .htaccess file (for changing to php5.2):
AddHandler application/x-httpd-php52 .php .php5 .php4 .php3
in the public_html root that would influence other directories recursively. (One can also do it differently in different directories if one needs that.)
After doing that the register_globals was off.