public function serialize()
    {
        $ns_string = '';
        foreach ($this->namespaces as $k => $v) {
            $ns_string .= "\n  xmlns:$k=\"$v\"";
        }
        $return_msg =
            '<?xml version="1.0" encoding="' . $this->soap_defencoding . '"?>' .
            '<SOAP-ENV:Envelope SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"' . $ns_string . ">\n" .
            '<SOAP-ENV:Body>' .
            '<SOAP-ENV:Fault>' .
            $this->serialize_val($this->faultcode, 'faultcode') .
            $this->serialize_val($this->faultactor, 'faultactor') .
            $this->serialize_val($this->faultstring, 'faultstring') .
            $this->serialize_val($this->faultdetail, 'detail') .
            '</SOAP-ENV:Fault>' .
            '</SOAP-ENV:Body>' .
            '</SOAP-ENV:Envelope>';
        return $return_msg;
    }