function ns_to_prefix($qname, $attr=false) {
# split 'http://www.w3.org/1999/xhtml:div' into ('http','//www.w3.org/1999/xhtml','div')
function ns_to_prefix($qname, $attr=false) {
# split 'http://www.w3.org/1999/xhtml:div' into ('http','//www.w3.org/1999/xhtml','div')