<?php
	$doc=new DOMDocument;
	$doc->loadXML('<params>
<param>
<value><array><data>
<value><string>Datum</string></value>
<value><string>27.07.2006</string></value>
</data></array></value>
</param>
<param>
<value><array><data>
<value><string>Uhrzeit</string></value>
<value><string>13:35:53</string></value>
</data></array></value>
</param>
<param>
<value><array><data>
<value><string>ErrorCode</string></value>
<value><string>200</string></value>
</data></array></value>
</param>
</params>');
$params=$doc->getElementsByTagName('param');
$arr=array();
for($p=0;$p<$params->length;++$p){
	$arr[$params->item($p)->getElementsByTagName('string')->item(0)->nodeValue]=
		$params->item($p)->getElementsByTagName('string')->item(1)->nodeValue;
}
var_dump($arr);	
	
?>

array(3) {
  ["Datum"]=>
  string(10) "27.07.2006"
  ["Uhrzeit"]=>
  string(8) "13:35:53"
  ["ErrorCode"]=>
  string(3) "200"
}