微信JS-SDK——微信分享给朋友

　　　　参考： 微信JS-SDK文档 其中包含有分享朋友圈、发送给朋友的js接口方法。（似乎不知道什么时候就会废弃）
　　　　文档中有完整的步骤，麻烦的是第三步：通过config接口注入权限验证配置。其中需要获取 signature(签名) ，必须通过服务器端才行。

　　　　本文主要是关于通过服务器获取签名的方法

　　授权需要获取access_token，然后通过access_token取到jsapi_ticket再进行加密签名。

　　微信公众号获取的access_token有两种：网页授权access_token、普通access_token，前者仅用于网页端请求用户授权，获取用户信息。后者则广泛用于微信各种接口。本文需要的就是后者：普通access_token。

　　（另外备注一点：网页授权获取access_token是先获取到(用户同意授权之后的)code，再根据code获取access_token，而普通access_token直接通过appid、appsecret，请求一次就可获得）

       主要是获取access_token的，以后再用直接复制就行

<?php

class weixin{
    private $AppID = '';//自行填写
    private $AppSecret = '';//自行填写

    public $tokenFile = './wxtoken.txt';//保存token的文件，有效期2小时
    public $jsapiFile = './wxjsapi_ticket.txt';//保存 jsapi_ticket的文件，有限期2小时
    public $getTokenUrl = 'https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=APPID&secret=APPSECRET';
    public $getjsapiUrl = 'https://api.weixin.qq.com/cgi-bin/ticket/getticket?access_token=ACCESS_TOKEN&type=jsapi';

    public function __construct(){
        $this->http_type = ((isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] == 'on') || (isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && $_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https')) ? 'https://' : 'http://';
    }

    public function index(){
      $action = isset($_GET['do']) ? $_GET['do'] : '';
      switch($action){
        case 'ApiJsSignature':
          $ret = $this->ApiJsSignature();//获取分享需要的签名等数据
          break;
        default:
          echo 'default';
          break;
      }
    }

    //用于微信分享到朋友圈或给朋友的参数
    public function ApiJsSignature(){
        $access_token = $this->get_access_token();
        $JsapiTicket = $this->get_jsapi_ticket($access_token);

        $signArr = array(
            'jsapi_ticket' => $JsapiTicket,
            'noncestr' => $this->str_rand(16),
            'timestamp' => time(),
            'url' => urldecode($_POST['jsapi_url'])
        );
        $signStr = 'jsapi_ticket='.$signArr['jsapi_ticket'].'&noncestr='.$signArr['noncestr'].'×tamp='.$signArr['timestamp'].'&url='.$signArr['url'];
        //http_build_query()这个方法好像有问题，我使用之后返回的参数缺少字符

        $signArr['signature'] = sha1($signStr);
        $signArr['appid'] = $this->AppID;
        echo json_encode($signArr);
    }


    //第二步获取jsapi_ticket
    public function get_jsapi_ticket($access_token) {
        if(!file_exists($this->jsapiFile)) {
            $JsapiTicket = $this->resetJsapiTicket($access_token);
        }else{
            $fileContent=file_get_contents($this->jsapiFile);
            $ticketArr = json_decode($fileContent,true);
            if($ticketArr['expires_in'] < time()) {
                $JsapiTicket = $this->resetJsapiTicket($access_token);
            }else{
                $JsapiTicket = $ticketArr['ticket'];
            }
        }
        return $JsapiTicket;
    }
    public function resetJsapiTicket($access_token) {
        $url = str_replace('ACCESS_TOKEN', $access_token, $this->getjsapiUrl);

        $ticketJson = $this->curlPost($url);
        $ticketData = json_decode($ticketJson, true);

        $ticketData['expires_in'] = $ticketData['expires_in']+time();
        file_put_contents($this->jsapiFile, json_encode($ticketData));

        return $ticketData['ticket'];
    }

    //第一步获取access_token
    public function get_access_token() {
        if(!file_exists($this->tokenFile)) {
            $access_token = $this->resetToken();//重置token并写入文件 , 返回token值
        }else{
            $fileContent=file_get_contents($this->tokenFile);
            $tokenArr = json_decode($fileContent,true);
            if($tokenArr['expires_in'] < time()) {
                $access_token = $this->resetToken();
            }else{
                $access_token = $tokenArr['access_token'];
            }
        }
        return $access_token;
    }
    //刷新、重置token, 设置获取token事件并将json数据写入文件,最后返回token值，
    private function resetToken(){
        $url = str_replace('APPID', $this->AppID, $this->getTokenUrl);
        $url = str_replace('APPSECRET', $this->AppSecret, $url);

        $tokenJson = $this->curlPost($url);
        $tokenData = json_decode($tokenJson, true);

        $tokenData['expires_in'] = $tokenData['expires_in']+time();
        file_put_contents($this->tokenFile, json_encode($tokenData));

        return $tokenData['access_token'];
    }

    //生成随机字符串
    public function str_rand($length = 32) {
        $char = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
        if(!is_int($length) || $length < 0) {
            return false;
        }
        $string = '';
        for($i = $length; $i > 0; $i--) {
            $string .= $char[mt_rand(0, strlen($char) - 1)];
        }
        return $string;
    }

    //发送请求
    public function curlPost($url, $data = '') {
        if (! function_exists('curl_init')) {
            return '';
        }

        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
        curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);

        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
        // curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($data)); // 可提交数组参数
        $data = curl_exec($ch);

        if (! $data) {
            error_log(curl_error($ch));
        }

        curl_close($ch);
        return $data;
    }
}

// 调用方式: index.php?do=ApiJsSignature
$weixin = new weixin();
$weixin->index();