XMLReader: missing rewind()

I'm missing a function like $reader->rewind() to set the internal cursor of the reader to its starting position. further i didn't found such rewind() at http://xmlsoft.org/html/libxml-xmlreader.html , the home of libxml's xmlreader... i think the only way getting out is to $reader->close() and $reader->XML(...) again?? Can somebody help me with that? thanks in advance vivian