Seeing the variable table / $conf array... and the invisible/latent settings configuration variables

the $conf variable --

http://api.drupal.org/api/drupal/developer--globals.php/global/conf/7

Tip To be sure to always have logging to the screen enabled in your test environment, you can add this to your local settings.php file: $conf['error_level'] = 2; // Set what level of warning and error messages are sent to the screen. You can see what values are presently in the variable table with debug($conf). However, variables which have never had their settings form saved – which are still at their default value – will not show up in the table or the $conf array. Instead, the fastest way to determine what the name of a configuration variable that is still using its unset default is to print out its settings page form