src/Didww/API2/ApiClient.php
public static function getWSDL()
    {
        if (!empty(self::$_wsdl)) {
            return self::$_wsdl;
        }
        return self::getCredentials()->getTestMode() ? self::SANDBOX_WSDL : self::PRODUCTION_WSDL;
    }
public static function getWSDL()
    {
        if (!empty(self::$_wsdl)) {
            return self::$_wsdl;
        }
        return self::getCredentials()->getTestMode() ? self::SANDBOX_WSDL : self::PRODUCTION_WSDL;
    }
return current wsdl url or url by production/sandbox mode
@return string