- var_dump: documentation ( source)
<?php
$xml = '<RESPONSE><FIELDS><FIELD KEY="MSG_VERSION">333</FIELD><FIELD KEY="CUST_NBR">222</FIELD><FIELD KEY="MERCH_NBR">111</FIELD></FIELDS></RESPONSE>';
$doc = new DOMDocument;
$doc->loadXml($xml);
$xpath = new DOMXPath($doc);
$query = '/RESPONSE/FIELDS/FIELD';
$entries = $xpath->evaluate($query, $doc);
var_dump($entries);