public function ToXml($data=array())
 {
 if(!is_array($data) || count($data) <= 0)
 {
  return '數組異常';
 }
 $xml = "<xml>";
 foreach ($data as $key=>$val)
 {
  if (is_numeric($val)){
  $xml.="<".$key.">".$val."</".$key.">";
  }else{
  $xml.="<".$key."><![CDATA[".$val."]]></".$key.">";
  }
 }
 $xml.="</xml>";
 return $xml;
 }

function rand_code(){
 $str = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';//62個字符
 $str = str_shuffle($str);
 $str = substr($str,0,32);
 return $str;
}

private function getSign($params) {
 ksort($params); //將參數數組按照參數名ASCII碼從小到大排序
 foreach ($params as $key => $item) {
  if (!empty($item)) {  //剔除參數值為空的參數
  $newArr[] = $key.'='.$item; // 整合新的參數數組
  }
 }
 $stringA = implode("&", $newArr);  //使用 & 符號連接參數
 $stringSignTemp = $stringA."&key="."************************"; //拼接key
 // key是在商戶平臺API安全里自己設置的
 $stringSignTemp = MD5($stringSignTemp); //將字符串進行MD5加密
 $sign = strtoupper($stringSignTemp); //將所有字符轉換為大寫
 return $sign;
 }

public function wx_pay() {
 $nonce_str = $this->rand_code(); //調用隨機字符串生成方法獲取隨機字符串
 $data['appid'] ='wxdbc5dc*******'; //appid
 $data['mch_id'] = '1493*****' ; //商戶號
 $data['body'] = "APP支付測試";
 $data['spbill_create_ip'] = $_SERVER['HTTP_HOST']; //ip地址
 $data['total_fee'] = 1;    //金額
 $data['out_trade_no'] = time().mt_rand(10000,99999); //商戶訂單號,不能重復
 $data['nonce_str'] = $nonce_str;   //隨機字符串
 $data['notify_url'] = 'http://xxx.xxx.com/wx_notify'; //回調地址,用戶接收支付后的通知,必須為能直接訪問的網址,不能跟參數
 $data['trade_type'] = 'APP'; //支付方式
 //將參與簽名的數據保存到數組 注意：以上幾個參數是追加到$data中的，$data中應該同時包含開發文檔中要求必填的剔除sign以外的所有數據
 $data['sign'] = $this->getSign($data); //獲取簽名
 $xml = $this->ToXml($data);  //數組轉xml
 //curl 傳遞給微信方
 $url = "https://api.mch.weixin.qq.com/pay/unifiedorder";
 //header("Content-type:text/xml");
 $ch = curl_init();
 curl_setopt($ch,CURLOPT_URL, $url);
 if(stripos($url,"https://")!==FALSE){
  curl_setopt($ch, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1);
  curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
  curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);
 } else {
  curl_setopt($ch,CURLOPT_SSL_VERIFYPEER,TRUE);
  curl_setopt($ch,CURLOPT_SSL_VERIFYHOST,2);//嚴格校驗
 }
 //設置header
 curl_setopt($ch, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1);
 curl_setopt($ch, CURLOPT_HEADER, FALSE);
 //要求結果為字符串且輸出到屏幕上
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
 //設置超時
 curl_setopt($ch, CURLOPT_TIMEOUT, 30);
 curl_setopt($ch, CURLOPT_POST, TRUE);
 //傳輸文件
 curl_setopt($ch, CURLOPT_POSTFIELDS, $xml);
 //運行curl
 $data = curl_exec($ch);
 //返回結果
 if($data){
  curl_close($ch);
  //返回成功,將xml數據轉換為數組.
  $re = $this->FromXml($data);
  if($re['return_code'] != 'SUCCESS'){
  json("201",'簽名失敗');
  }
  else{
  //接收微信返回的數據,傳給APP!
  $arr =array(
   'prepayid' =>$re['prepay_id'],
   'appid' => 'wxdbc5dc*****',
   'partnerid' => '14937****',
   'package' => 'Sign=WXPay',
   'noncestr' => $nonce_str,
   'timestamp' =>time(),
  );
  //第二次生成簽名
  $sign = $this->getSign($arr);
  $arr['sign'] = $sign;
  json('200','簽名成功',$arr);
  }
 } else {
  $error = curl_errno($ch);
  curl_close($ch);
  json('201',"curl出錯，錯誤碼:$error");
 }
 }

public function FromXml($xml)
 {
 if(!$xml){
  echo "xml數據異常！";
 }
 //將XML轉為array
 //禁止引用外部xml實體
 libxml_disable_entity_loader(true);
 $data = json_decode(json_encode(simplexml_load_string($xml, 'SimpleXMLElement', LIBXML_NOCDATA)), true);
 return $data;
 }