<?php
namespace App\Common ;

use Exception;

class WechatPay {

    /**
     * WechatPay constructor.
     */
    public function __construct()
    {
        $this->config  = [
            'appid'       => env('WECHAT_APPID'),//小程序appid
            'pay_mchid'   => env('MCH_ID'),//商户号
            'pay_apikey'  => env('MCH_KEY'),//可在微信商户后台生成支付秘钥
        ];
    }

    /**
     * 统一下单
     * @author
     * @since 1.0
     * @param $openid
     * @param $total_fee
     * @param $outTradeNo
     * @param $body
     * @param $clientIp
     * @return array
     * @throws Exception
     * @internal param $totalPrice
     * @internal param $describe
     */
    public function unifiedorder($openid,$total_fee,$outTradeNo,$body,$clientIp)
    {
        $config = $this->config ;
        //统一下单参数构造
        $unifiedorder = array(
            'appid'            => $config['appid'],
            'mch_id'        => $config['pay_mchid'],
            'nonce_str'        => self::getNonceStr(),
            'body'            => $body,
            'out_trade_no'    => $outTradeNo,
            'total_fee'        => $total_fee * 100,
            'spbill_create_ip'    => $clientIp,
            'notify_url'    => 'https://HOSTNAME/wechat/payNotify',// 支付微信回调的url，可自定义,非必须
            'trade_type'    => 'JSAPI',
            'openid'        => $openid,
        );
        $unifiedorder['sign'] = self::makeSign($unifiedorder);
        //请求数据
        $xmldata = self::array2xml($unifiedorder);
        $url = 'https://api.mch.weixin.qq.com/pay/unifiedorder';
        $res = self::curl_post_ssl($url, $xmldata);
        if(!$res){
            throw new Exception('无法连接服务器',10001);
        }
        //file_put_contents是用来查看服务器返回的结果 测试完可以删除了,可以使用laravel自带日志功能
        \Log::info(json_encode($res));
        $content = self::xml2array($res);
        $result_code= isset($content['result_code']) ? $content['result_code'] : '';
        $return_code = isset($content['return_code']) ? $content['return_code'] : '';
        if(strval($result_code) == 'FAIL'){
            throw new Exception(strval($content['err_code_des']),10001);
        }
        if(strval($return_code) == 'FAIL'){
            throw new Exception(strval($content['return_msg']),10001);
        }
        return $content['prepay_id'] ;
    }


    /**
     * 进行支付接口签名
     * @param string $prepay_id 预支付ID(调用prepay()方法之后的返回数据中获取)
     * @return  json的数据
     */
    public function pay($prepay_id){
        $config = $this->config;
        $data = array(
            'appId'        => $config['appid'],
            'timeStamp'    => time(),
            'nonceStr'    => self::getNonceStr(),
            'package'    => 'prepay_id='.$prepay_id,
            'signType'    => 'MD5'
        );

        $data['paySign'] = self::makeSign($data);

        return $data;
    }


    //---------------------------------------------------------------用到的函数------------------------------------------------------------

    /**
     * 将一个数组转换为 XML 结构的字符串
     * @param array $arr 要转换的数组
     * @param int $level 节点层级, 1 为 Root.
     * @return string XML 结构的字符串
     */
    protected function array2xml($arr, $level = 1) {
        $s = $level == 1 ? "<xml>" : '';
        foreach($arr as $tagname => $value) {
            if (is_numeric($tagname)) {
                $tagname = $value['TagName'];
                unset($value['TagName']);
            }
            if(!is_array($value)) {
                $s .= "<{$tagname}>".(!is_numeric($value) ? '<![CDATA[' : '').$value.(!is_numeric($value) ? ']]>' : '')."</{$tagname}>";
            } else {
                $s .= "<{$tagname}>" . $this->array2xml($value, $level + 1)."</{$tagname}>";
            }
        }
        $s = preg_replace("/([\x01-\x08\x0b-\x0c\x0e-\x1f])+/", ' ', $s);
        return $level == 1 ? $s."</xml>" : $s;
    }

    /**
     * 将xml转为array
     * @param  string     $xml xml字符串
     * @return array    转换得到的数组
     */
    protected function xml2array($xml){
        //禁止引用外部xml实体
        libxml_disable_entity_loader(true);
        $result= json_decode(json_encode(simplexml_load_string($xml, 'SimpleXMLElement', LIBXML_NOCDATA)), true);
        return $result;
    }

    /**
     *
     * 产生随机字符串，不长于32位
     * @param int $length
     * @return 产生的随机字符串
     */
    protected function getNonceStr($length = 32) {
        $chars = "abcdefghijklmnopqrstuvwxyz0123456789";
        $str ="";
        for ( $i = 0; $i < $length; $i++ )  {
            $str .= substr($chars, mt_rand(0, strlen($chars)-1), 1);
        }
        return $str;
    }

    /**
     * 生成签名
     * @return 签名
     */
    protected function makeSign($data){
        //获取微信支付秘钥
        $key = $this->config['pay_apikey'];
        // 去空
        $data=array_filter($data);
        //签名步骤一：按字典序排序参数
        ksort($data);
        $string_a=http_build_query($data);
        $string_a=urldecode($string_a);
        //签名步骤二：在string后加入KEY
        $string_sign_temp=$string_a."&key=".$key;
        //签名步骤三：MD5加密
        $sign = md5($string_sign_temp);
        // 签名步骤四：所有字符转为大写
        $result=strtoupper($sign);
        return $result;
    }

    /**
     * 微信支付发起请求
     */
    protected function curl_post_ssl($url, $xmldata, $second=30,$aHeader=array()){
        $ch = curl_init();
        //超时时间
        curl_setopt($ch,CURLOPT_TIMEOUT,$second);
        curl_setopt($ch,CURLOPT_RETURNTRANSFER, 1);
        //这里设置代理，如果有的话
        //curl_setopt($ch,CURLOPT_PROXY, '10.206.30.98');
        //curl_setopt($ch,CURLOPT_PROXYPORT, 8080);
        curl_setopt($ch,CURLOPT_URL,$url);
        curl_setopt($ch,CURLOPT_SSL_VERIFYPEER,false);
        curl_setopt($ch,CURLOPT_SSL_VERIFYHOST,false);


        if( count($aHeader) >= 1 ){
            curl_setopt($ch, CURLOPT_HTTPHEADER, $aHeader);
        }

        curl_setopt($ch,CURLOPT_POST, 1);
        curl_setopt($ch,CURLOPT_POSTFIELDS,$xmldata);
        $data = curl_exec($ch);
        if($data){
            curl_close($ch);
            return $data;
        }
        else {
            $error = curl_errno($ch);
            echo "call faild, errorCode:$error\n";
            curl_close($ch);
            return false;
        }
    }

}

调用方法