Hi I think the SimpleXml is very useful .
And with it I am using xpath;
$xml = simplexml_load_file("som_xml.xml");
$blocks = $xml->xpath('//block'); //gets all tags
$blocks2 = $xml->xpath('//layout/block'); //gets all which parent are tags
I use many xml configs and this helps me to parse them really fast.
SimpleXml is written on C so it's very fast.