There seems to be an undocumented function svn_info (arguably the proper name for this functionality) that does almost the same as svn_status, but ignores the second parameter.
Unfortunately, neither can directly be used to just retrieve the current revision of a working copy, but a combination of svn_status and SVN_NON_RECURSIVE|SVN_ALL will work; simply perform the following command:
<?php
svn_status(ROOT, SVN_NON_RECURSIVE|SVN_ALL);
?>
Where ROOT is of course the root of the working directory you wish to examine. One of the entries will be that working directory, including its current status.
