int xmlReaderGetDepth(xmlReader reader)
xmlReaderGetDepth() returns how many elements deep the reader's current
position is, where the root element is 1, its children are 2, its
children's children are 3, etc.
<$depth = (xmlReaderGetDepth($reader))>
xmlReader parser can read ahead and buffer some of the
XML message, so functions like this might not match the current