微信开发所需要的的方法（签名认证、数组转字符串方法、将xml字符串转换为数组、发送xml请求方法）

    //将xml字符串转换为数组
    public function xmlToArray($xml){
        $array_data = json_decode(json_encode(simplexml_load_string($xml, 'SimpleXMLElement', LIBXML_NOCDATA)), true);
        return $array_data;
    }

    /*
    * 对要发送到微信统一下单接口的数据进行签名
    */
    public function getSign($Obj,$apiKey){
        foreach ($Obj as $k => $v){
            $param[$k] = $v;
        }
        //签名步骤一：按字典序排序参数
        ksort($param);
        $String = $this->formatBizQueryParaMap($param, false);
        //签名步骤二：在string后加入KEY
        $String = $String."&key=" . $apiKey;
        //签名步骤三：MD5加密
        $String = md5($String);
        //签名步骤四：所有字符转为大写
        $result_ = strtoupper($String);
        return $result_;
    }

    /*
    *排序并格式化参数方法，签名时需要使用
    */
    public function formatBizQueryParaMap($paraMap, $urlencode)
    {
        $buff = "";
        ksort($paraMap);
        foreach ($paraMap as $k => $v)
        {
            if($urlencode)
            {
                $v = urlencode($v);
            }
            //$buff .= strtolower($k) . "=" . $v . "&";
            $buff .= $k . "=" . $v . "&";
        }
        $reqPar = "";
        if (strlen($buff) > 0)
        {
            $reqPar = substr($buff, 0, strlen($buff)-1);
        }
        return $reqPar;
    }

    //数组转字符串方法
    public function arrayToXml($arr){
        $xml = "<xml>";
        foreach ($arr as $key=>$val)
        {
            if (is_numeric($val)){
                $xml.="<".$key.">".$val."</".$key.">";
            }else{
                $xml.="<".$key."><![CDATA[".$val."]]></".$key.">";
            }
        }
        $xml.="</xml>";
        return $xml;
    }

    //发送xml请求方法
    private static function postXmlCurl($xml, $url, $second = 30)
    {
        $ch = curl_init();
        //设置超时
        curl_setopt($ch, CURLOPT_TIMEOUT, $second);
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
        curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE); //严格校验
        //设置header
        curl_setopt($ch, CURLOPT_HEADER, FALSE);
        //要求结果为字符串且输出到屏幕上
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
        //post提交方式
        curl_setopt($ch, CURLOPT_POST, TRUE);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $xml);
        curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 20);
        curl_setopt($ch, CURLOPT_TIMEOUT, 40);
        set_time_limit(0);
        //运行curl
        $data = curl_exec($ch);
        //返回结果
        if ($data) {
            curl_close($ch);
            return $data;
        } else {
            $error = curl_errno($ch);
            curl_close($ch);
            throw new WxPayException("curl出错，错误码:$error");
        }
    }

    //生成随机数字
    function getNonceNums($numLen = 4)
    {
        $chars = "0123456789";
        $str = "";
        for ($i = 0; $i < $numLen; $i++) {
            $str .= substr($chars, mt_rand(0, strlen($chars) - 1), 1);
        }
        return $str;
    }

    /*
    * 生成随机字符串方法
    */
    public function createNoncestr($length = 32)
    {
        $chars = "abcdefghijklmnopqrstuvwxyz0123456789";
        $str = "";
        for ($i = 0; $i < $length; $i++) {
            $str .= substr($chars, mt_rand(0, strlen($chars) - 1), 1);
        }
        return $str;
    }