$xmlDoc=<<<XML
<?xml version="1.0"?>
<methodCall>
   <methodName>examples.getStateName</methodName>
   <params>
      <param>
         <value><i4>41</i4></value>
         </param>
      </params>
   </methodCall>
XML;

$xml= new DOMDocument();
$xml->preserveWhiteSpace=false;
$xml->loadXML($xmlDoc);
print_r(xml2array($xml));

function xml2array($n)
{
    $return=array();
    foreach($n->childNodes as $nc)
    ($nc->hasChildNodes())
    ?($n->firstChild->nodeName== $n->lastChild->nodeName&&$n->childNodes->length>1)
    ?$return[$nc->nodeName][]=xml2array($item)
    :$return[$nc->nodeName]=xml2array($nc)
    :$return=$nc->nodeValue;
    return $return;
}