I made a slightly differnt approch towards the RecurseXML function. Beeing hungry I had problems with the code, as it did just overwrite two <maincourse>s. So here is what I did:
<?php
$xml = new SimpleXMLElement(
'<meal>
   <type>Lunch</type>
   <time>12:30</time>
   <menu>
     <entree>salad</entree>
     <maincourse>
        <part>ships</part>
        <part>steak</part>
     </maincourse>
     <maincourse>
        <part>fisch</part>
        <part>rice</part>
     </maincourse>
     <maincourse>
        <part>wine</part>
        <part>cheese</part>
     </maincourse>
   </menu>
</meal>');
$vals = array();
RecurseXML($xml,$vals);
foreach($vals as $key=>$value)
  print("{$key} = {$value}<BR>\n");
function RecurseXML($xml,&$vals,$parent="") {
  $childs=0;
  $child_count=-1; $arr=array();
        foreach ($xml->children() as $key=>$value) {
                if (in_array($key,$arr)) {
                        $child_count++;
                } else {
                        $child_count=0;
                }
                $arr[]=$key;
                $k=($parent == "") ? "$key.$child_count" : "$parent.$key.$child_count";
                $childs=RecurseXML($value,$vals,$k);
                if ($childs==0) {
                        $vals[$k]= (string)$value;
                }
        }
  return $childs;
}
?>
Output is like this:
type.0 = Lunch
time.0 = 12:30
menu.0.entree.0 = salad
menu.0.maincourse.0.part.0 = ships
menu.0.maincourse.0.part.1 = steak
menu.0.maincourse.0 =
menu.0.maincourse.1.part.0 = fisch
menu.0.maincourse.1.part.1 = rice
menu.0.maincourse.1 =
menu.0.maincourse.2.part.0 = wine
menu.0.maincourse.2.part.1 = cheese
menu.0.maincourse.2 =
menu.0 = 
(Not beautiful, but it solved my case...)