From Joomla! Documentation
The "API15" namespace is an archived namespace. This page contains information for a Joomla! version which is no longer supported. It exists only as a historical reference, it will not be improved and its content may be incomplete and/or contain broken links.
|stringToObject||Converts an XML formatted string into an object|
|objectToString||Converts an object into an XML formatted string
If more than two levels of nested groups are necessary, since INI is not useful, XML or another format should be used.
jimport( 'joomla.registry.format.xml' );