SoapHeader is a special low-level class for passing
or returning SOAP headers. It's just a data holder and it does not have any
special methods except its constructor. It can be used in the SoapClient->__soapCall method to pass a SOAP header or
in a SOAP header handler to return the header in a SOAP response.
SoapVar is a special low-level class for encoding
parameters and returning values in non-WSDL mode. It's
just a data holder and does not have any special methods except the constructor.
It's useful when you want to set the type property in SOAP request or response.