class Wxpay {
    /*
    配置引數
    */
    private $config = array(
        'appid' => "wxc888888888",    /*微信開放平臺上的應用id*/
        'mch_id' => "88888888",   /*微信申請成功之後郵件中的商戶id*/
        'api_key' => "5d82747060a5873e0d3de256b8485094",    /*在微信商戶平臺上自己設定的api金鑰 32位*/
        'notify_url' => 'http://www.xxxxx.com/app/index.php/Api/modifyPayState' /*自定義的回撥程式地址*/
    );
 
 
     //下單
    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);
 
        //將微信返回的結果xml轉成陣列
        $response = $this->xmlToArray($response);
 
        //返回資料
        return $respone;
    }
 
　　/*生成簽名*/
    public function getSign($Obj){
        foreach ($Obj as $k => $v){
            $Parameters[$k] = $v;
        }
        //簽名步驟一：按字典序排序引數
        ksort($Parameters);
        $String = $this->formatBizQueryParaMap($Parameters, false);
        //echo '【string1】'.$String.'</br>';
        //簽名步驟二：在string後加入KEY
        $String = $String."&key=".$this->config['api_key'];
        //echo "【string2】".$String."</br>";
        //簽名步驟三：MD5加密
        $String = md5($String);
        //echo "【string3】 ".$String."</br>";
        //簽名步驟四：所有字元轉為大寫
        $result_ = strtoupper($String);
        //echo "【result】 ".$result_."</br>";
        return $result_;
    }
 
 
    /**
    *  作用：產生隨機字串，不長於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;
    }
 
 
    //陣列轉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：將xml轉為array
    */
    public function xmlToArray($xml){  
        //將XML轉為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到對應的介面url
    */
    public function postXmlCurl($xml,$url,$second=30){  
        //初始化curl       
        $ch = curl_init();
        //設定超時
        curl_setopt($ch, CURLOPT_TIMEOUT, $second);
        //這裡設定代理，如果有的話
        //curl_setopt($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($ch,CURLOPT_SSL_VERIFYHOST,FALSE);
        //設定header
        curl_setopt($ch, CURLOPT_HEADER, FALSE);
        //要求結果為字串且輸出到螢幕上
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
        //post提交方式
        curl_setopt($ch, CURLOPT_POST, TRUE);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $xml);
        //執行curl
        $data = curl_exec($ch);
        //返回結果
 
        if($data){
            curl_close($ch);
            return $data;
        }else{
            $error = curl_errno($ch);
            echo "curl出錯，錯誤碼:$error"."<br>";
            curl_close($ch);
            return false;
        }
    }
 
 
    /*
    獲取當前伺服器的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：格式化引數，簽名過程需要使用
    */
    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;
    }