( mixed obj )
This function is useful when you like to check if the SOAP call failed, but
don't like to use exceptions. To use it you must create a
SoapClient object with the exceptions
option set to zero or FALSE.
In this case, the SOAP method will return a special
SoapFault object which encapsulates the fault
details (faultcode, faultstring, faultactor and faultdetails).
If exceptions is not set then SOAP call will throw
an exception on error.
is_soap_fault() checks if the given
parameter is a SoapFault object.