I think you're confusing two completely independent constructs.
Variable_get and variable_set are used to store system wide settings that should persist in the database. They are never (to my knowledge) instantiated as PHP variables. The caching structure is meant to reduce the number of database hits involved in loading variables, and should not generally be accessed directly. Multiple calls to variable_get should leverage the cached variables as appropriate.
The variables in settings.php can be used, you can define your own global variables there, but if you want them to persist between page loads you need to do that yourself. IN your hooks you can reference these variables after defining them as globals, but be careful with namespace collisions. I usually create a global variable that has the same name as my module and store everying inside it (as an associative array).
Finally session variables can be used and will persist in the database for the duration of a session.
Hope that clarifies things. It sounds like drupal is behaving as designed here.
Dave
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From: support-bounces@drupal.org [mailto:support-bounces@drupal.org] On Behalf Of Scott Matthews Sent: Tuesday, January 29, 2008 7:37 AM To: support@drupal.org Cc: Ron Trevarrow Subject: [support] Issues with initializing Variables on startup..
I found what Appears to be a bug (or two) with initializing variables in Drupal.
It is suggested that you can uncomment and set initial variable values in settings.php with the $conf array. In doing so, and not seeing my variables set when retrieving using variable_get, I discovered that conf_init(), when called to initialize the configure file path, it sets $conf to a string. I know that since it initializes settings.php within the context it conceptually SHOULD reset it to a variable, but it doesn't. I proved this by changing the variable array name in settings.php, variable_get, variable_set, variable_init and conf_init to $config_vars and the values I initialized in settings.php were reflected when my application later retrieved them using variable_get.
This bug is currently hindering the flexibility of an application that I'm writing that will be deployed to different environments. I initially tried to set the variables in the 'variable' table of the Database in order to retrieve them with variable_get but that method only accesses the cached variables in $conf (or in my case, $config_vars. Is this on purpose? I see that variable_set will not only set the cached variable but will also set into the database. This seems to be a bug as well to me. Can someone clarify this for me?
Scott Matthews