class Wxpay {

    /*

    配置参数

    */

    private $config = array(

        'appid' => "wxc888888888",    /*微信开放平台上的应用id*/

        'mch_id' => "88888888",   /*微信申请成功之后邮件中的商户id*/

        'api_key' => "5d82747060a5873e0d3de256b8485094",    /*在微信商户平台上自己设定的api密钥 32位*/

        'notify_url' => 'http://www.xxxxx.com/app/index.php/Api/modifyPayState' /*自定义的回调程序地址*/

    );

     //下单

    public function getPrePayOrder($body, $out_trade_no, $total_fee){

        $url = "https://api.mch.weixin.qq.com/pay/unifiedorder";

        $notify_url = $this->config["notify_url"];

        $onoce_str = $this->createNoncestr();

        $data["appid"] = $this->config["appid"];

        $data["body"] = $body;

        $data["mch_id"] = $this->config['mch_id'];

        $data["nonce_str"] = $onoce_str;

        $data["notify_url"] = $notify_url;

        $data["out_trade_no"] = $out_trade_no;

        $data["spbill_create_ip"] = $this->get_client_ip();

        $data["total_fee"] = $total_fee;

        $data["trade_type"] = "APP";

        $sign = $this->getSign($data);

        $data["sign"] = $sign;

        $xml = $this->arrayToXml($data);

        $response = $this->postXmlCurl($xml, $url); 

        //将微信返回的结果xml转成数组

        $response = $this->xmlToArray($response);

        //返回数据

        return $respone;

    }

　　/*生成签名*/

    public function getSign($Obj){

        foreach ($Obj as $k => $v){

            $Parameters[$k] = $v;

        }

        //签名步骤一：按字典序排序参数

        ksort($Parameters);

        $String = $this->formatBizQueryParaMap($Parameters, false);

        //echo '【string1】'.$String.'</br>';

        //签名步骤二：在string后加入KEY

        $String = $String."&key=".$this->config['api_key'];

        //echo "【string2】".$String."</br>";

        //签名步骤三：MD5加密

        $String = md5($String);

        //echo "【string3】 ".$String."</br>";

        //签名步骤四：所有字符转为大写

        $result_ = strtoupper($String);

        //echo "【result】 ".$result_."</br>";

        return $result_;

    }

    /**

    *  作用：产生随机字符串，不长于32位

    */

    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;

    }

    //数组转xml

    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;

    }

    /**

    *  作用：将xml转为array

    */

    public function xmlToArray($xml){

        //将XML转为array

        $array_data = json_decode(json_encode(simplexml_load_string($xml, 'SimpleXMLElement', LIBXML_NOCDATA)), true);

        return $array_data;

    }

    /**

    *  作用：以post方式提交xml到对应的接口url

    */

    public function postXmlCurl($xml,$url,$second=30){

        //初始化curl

        $ch = curl_init();

        //设置超时

        curl_setopt($ch, CURLOPT_TIMEOUT, $second);

        //这里设置代理，如果有的话

        //curl_setopt($ch,CURLOPT_PROXY, '8.8.8.8');

        //curl_setopt($ch,CURLOPT_PROXYPORT, 8080);

        curl_setopt($ch,CURLOPT_URL, $url);

        curl_setopt($ch,CURLOPT_SSL_VERIFYPEER,FALSE);

        curl_setopt($ch,CURLOPT_SSL_VERIFYHOST,FALSE);

        //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);

        //运行curl

        $data = curl_exec($ch);

        //返回结果

        if($data){

            curl_close($ch);

            return $data;

        }else{

            $error = curl_errno($ch);

            echo "curl出错，错误码:$error"."<br>";

            curl_close($ch);

            return false;

        }

    }

    /*

    获取当前服务器的IP

    */

    public function get_client_ip(){

        if ($_SERVER['REMOTE_ADDR']) {

            $cip = $_SERVER['REMOTE_ADDR'];

        } elseif (getenv("REMOTE_ADDR")) {

            $cip = getenv("REMOTE_ADDR");

        } elseif (getenv("HTTP_CLIENT_IP")) {

            $cip = getenv("HTTP_CLIENT_IP");

        } else {

            $cip = "unknown";

        }

        return $cip;

    }

    /**

    *  作用：格式化参数，签名过程需要使用

    */

    public function formatBizQueryParaMap($paraMap, $urlencode){

        $buff = "";

        ksort($paraMap);

        foreach ($paraMap as $k => $v){

            if($urlencode){

                $v = urlencode($v);

            }

            $buff .= $k . "=" . $v . "&";

        }

        $reqPar;

        if (strlen($buff) > 0){

            $reqPar = substr($buff, 0, strlen($buff)-1);

        }

        return $reqPar;

    }