1. The soapClient member variable should be declared with a scope modifier, not the old-style 'var' keyword.
2. Use @return boolean instead of @return true|false
3. __soapCall didn't exist until PHP 5.0.2
4. in debug, !(isset($this->soapClient) && is_object($this->soapClient)) could be !($this->soapClient instanceof SoapClient)
5. Catching Exception around your SOAP calls is probably too broad. You're really interested in handling SoapFault exceptions.