//将xml转为array
    private function fromXml($xml){
        // 禁止引用外部xml实体
        libxml_disable_entity_loader(true);
        return json_decode(json_encode(simplexml_load_string($xml,'SimpleXMLElement',LIBXML_NOCDATA)),true);
    }    //输出xml字符
    private function toXml($values){
        if (!is_array($values)
            || count($values) <= 0
        ) {
            return false;
        }

        $xml = "<xml>";
        foreach ($values as $key => $val) {
            if (is_numeric($val)) {
                $xml .= "<" . $key . ">" . $val . "</" . $key . ">";
            } else {
                $xml .= "<" . $key . "><![CDATA[" . $val . "]]></" . $key . ">";
            }
        }
        $xml .= "</xml>";
        return $xml;
    }

         写日志
        private function doLogs($values){
        return write_log($values,__DIR__);
    }
     
     微信支付回调无法结束，解决方法
    echo exit('<xml><return_code><![CDATA[SUCCESS]]></return_code><return_msg><![CDATA[OK]]></return_msg></xml>');