$client->SomeFunction vs. $client->__soapCall("SomeFunction" ...)

Granted, I am relatively new to SoapClient but my understanding is that:

 $client->GetWeatherByZipCode( array('ZipCode' => '54601'));

 $client->__soapCall("GetWeatherByZipCode", array('ZipCode' => '54601'));

are equivalent. (I am hitting a weather service:
http://www.webservicex.net/WeatherForecast.asmx?wsdl )

However, the first works just fine, while the service chokes on the latter,
reporting
that the parameter "@zipCode" is not present.

Am I wrong in thinking the two requests above are equivalent and, if so,
what
am I missing?

Alo



-- 
Rob Gordon