<?php
require_once "jssdk.php";
$jssdk = new JSSDK("你的appId", "你的appSecret");
$signPackage = $jssdk->GetSignPackage();

$data = array(
 'appId' => $signPackage["appId"], 
 'timestamp' => $signPackage["timestamp"],
 'nonceStr' => $signPackage["nonceStr"],
 'signature' => $signPackage["signature"]);
echo json_encode($data);

<script src="http://res.wx.qq.com/open/js/jweixin-1.0.0.js"></script>
<script>
 $(function(){
  $.ajax({
    type: "GET",
    url: "./myapi.php",
    data: "",
    success: function(data){
     var result = JSON.parse(data);    
     if (result != null) { 
      wx.config({ 
       debug: false, 
       appId: result.appId, 
       timestamp: result.timestamp, 
       nonceStr: result.nonceStr, 
       signature: result.signature, 
       jsApiList: ['onMenuShareTimeline', 'onMenuShareAppMessage'] 
     }); 
     } 
    },
    error: function(){

    }
   });
 });

 window.sharedata = {
  title: '标题',
  desc: '描述',
  link: window.location.href,
  imgUrl: 'https://gqrcode.alicdn.com/img?type=cs&shop_id=295323332&seller_id=1094878600&w=140&h=140&el=q&v=1',
  success: function () {
   alert('success');
  },
  cancel: function () {
   alert('cancel');
  }
 };

 wx.ready(function () {
  wx.onMenuShareAppMessage(sharedata);
  wx.onMenuShareTimeline(sharedata);
 });

</script>