query apache for rewrite/alias rules

Hello,


Is there a way for PHP to "ask" apache for the result of a rewrite or
alias rule?

For instance, I have an Apache rule that alias /backup to /
systemBackup/archive1

Does PHP/Apache have any mechanism to retrieve the actual file system
location of /backup?


I would envision something like this:




to return

/systemBackup/archive1/someFile

and

$_SERVER['DOCUMENT_ROOT) ? 'true' : 'false' ?>

to return

true


Thoughts?

Thanks, CF