I would have to say that xml_parse_into_struct/COLOR would be the best option to get just a couple of node values from an xml document. Here's a generic example:
$file = "/path/to/xml_file";
$xml_data = implode('', file($file));
$xml_parser = xml_parser_create();
if (!xml_parse_into_struct($xml_parser, $xml_data, $vals, $index)) {
die(sprintf("syntax error: %s at XML input line %d in %s\n",
xml_error_string(xml_get_error_code($xml_parser)),
xml_get_current_line_number($xml_parser),
$file));
}
xml_parser_free($xml_parser);
echo "Index array\n";
print_r($index);
echo "\nVals array\n";
print_r($vals);
This will create 2 parallel arrays, one (index) containing pointers to the location of the appropriate values in the values array.
Some good, more complete examples are listed in thwe manual at http://www.php.net/manual/en/function.xml-parse-into-struct.php