The new DB XML offers now a PHP API:
Sleepycat Software is pleased to announce the release of Berkeley DB XML
version 1.2.1! DB XML 1.2.1 is a maintenance/bug fix release.New Features
A PHP API has been added to the distribution. This is a
preliminary release of this functionality. For details please
see the src/php4/README file contained in the distribution.
[1] http://www.merrells.com/john/dbxml/archives/cat_release_history.html#000229