I have the following XML ( you can say SOAP request ) :

<SOAPENV:Envelope xmlns:SOAPENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:NS="http://xyz.gov/headerschema" >
    <SOAPENV:Header>
        <NS:myHeader>
            <NS:SourceID>223423</NS:SourceID>
        </NS:myHeader>
    </SOAPENV:Header>
</SOAPENV:Envelope>

I use the following code and it works fine :

<?php 
$myRequest ='<SOAPENV:Envelope xmlns:SOAPENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:NS="http://xyz.gov/headerschema" >
   <SOAPENV:Header>
      <NS:myHeader>
         <NS:SourceID>223423</NS:SourceID>
      </NS:myHeader>
   </SOAPENV:Header>
   </SOAPENV:Envelope>';
$xml = simplexml_load_string($myRequest, NULL, NULL, "http://schemas.xmlsoap.org/soap/envelope/");
$namespaces = $xml->getNameSpaces(true);

$soapHeader = $xml->children($namespaces['SOAPENV'])->Header;
$myHeader = $soapHeader->children($namespaces['NS'])->myHeader;
echo (string)$myHeader->SourceID;
?>

The Problem

I know the prefix ( SOAPENV + NS ) , but the clients could change the prefix to whatever they want, so they may send me xml document that has ( MY-SOAPENV + MY-NS) prefixes.

My Question

How can I handle this since the namespace prefixes are not static , how can I parse it ?

Thanks