<s:element name="PN_SET_BUDGET">
  <s:complexType>
    <s:sequence>
      <s:element minOccurs="0" maxOccurs="1" name="budgets">
        <s:complexType mixed="true">
          <s:sequence>
            <s:any/>
          </s:sequence>
        </s:complexType>
      </s:element>
      <s:element minOccurs="1" maxOccurs="1" name="integration_id" type="s:int"/>
    </s:sequence>
  </s:complexType>
</s:element>

struct PN_SET_BUDGET {
 budgets budgets;
 int integration_id;
}
struct budgets {
 <anyXML> any;
}

$xmlr = new SimpleXMLElement("<BUDGET></BUDGET>");
$xmlr->addChild('Business_Unit', '11111');
$xmlr->addChild('Gl_Account', '22222.00000');
$xmlr->addChild('Period_Month', '3');
$xmlr->addChild('Period_Year', '2010');
$xmlr->addChild('Amount', '444.00');
$wsdl_url = .....;
$params = new stdClass();
$params->budgets = $xmlr->asXML();
$params->integration_id = 1;
$client = new SoapClient($wsdl_url);
$client->PN_SET_BUDGET($params);

System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at MyWs.PN_SET_BUDGET(XmlDocument budgets, Int32 integration_id)
   --- End of inner exception stack trace ---