XML_Serializer serializes complex data structures like arrays or object
as XML documents.
This class helps you generating any XML document you require without the
need for DOM.
Furthermore this package can be used as a replacement to serialize() and
unserialize() as it comes with a matching XML_Unserializer that is able to 
create PHP data strcutures (like arrays and objects) from XML documents,
if type hints are available.

If you use the XML_Unserialzer on standard XML files, it will try to guess
how it has to be unserialized. In most cases it does exactly what you 
expect it to do.
Try reading a RSS file with XML_Unserializer and you have the whole RSS
file in a structured array or even a collection of objects, similar to 
XML_RSS.

Since version 0.8 the package is able to treat XML documents like the
simplexml extension of PHP 5.

WWW: http://pear.php.net/package/XML_Serializer/
