PHP Soapclient xsi:type in response

I'm calling a method in a SOAP server, and the response includes the following XML tag:

<SelctedSupplements>
    <Supplement xsi:type="PerRoomSupplement" suppId="1000680" suppName="Upgrade" supptType="4" suppIsMandatory="true" suppChargeType="Included" price="0.00" publishPrice="0.00"/>
</SelctedSupplements>

The result I'm getting is the following:

object(stdClass)#156 (1) {
  ["Supplement"]=>
  object(stdClass)#157 (7) {
    ["suppId"]=> int(1000680)
    ["suppName"]=> string(7) "Upgrade"
    ["supptType"]=> int(4)
    ["suppIsMandatory"]=> bool(true)
    ["suppChargeType"]=> string(8) "Included"
    ["price"]=> string(4) "0.00"
    ["publishPrice"]=> string(4) "0.00"
  }
}

So all of the attributes are there, except for xsi:type="PerRoomSupplement". How do I get xsi:type of the Supplement tag? Do I have to get the last XML response and parse it through an XML library?

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Before I submitted the question, I did some googling, and found a way to accomplish what I want, it may not be the ideal answer, but it does what I want. Here it is in case someone else is struggling with the same issue:

I know that the possible types of the Supplement tag are either PerRoomSupplement or PerPersonSupplement. What I did is create two classes with those names, and then map the SOAP response classes to my PHP classes. This way, I can easily know which type the supplement is (by using the get_class function)

class PerRoomSupplement{}
class PerPersonSupplement{}
$client = new SoapClient($url, array("classmap" => array(
    "PerRoomSupplement" => "PerRoomSupplement",
    "PerPersonSupplement" => "PerPersonSupplement"
)));

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Thanks,