header('content-type:text/html;charset=utf-8');

define("TOKEN", "my_weixin"); //define your token
$wx = new wechatCallbackapiTest();

if($_GET['echostr']){
 $wx->valid(); //如果发来了echostr则进行验证
}else{
 $wx->responseMsg(); //如果没有echostr，则返回消息
}


class wechatCallbackapiTest{

 public function valid(){ //valid signature , option

  $echoStr = $_GET["echostr"];
  if($this->checkSignature()){ //调用验证字段
   echo $echoStr;
   exit;
  }
 }

 public function responseMsg(){
  
 //get post data, May be due to the different environments
  $postStr = $GLOBALS["HTTP_RAW_POST_DATA"]; //接收微信发来的XML数据

  //extract post data
 if(!empty($postStr)){
    
   //解析post来的XML为一个对象$postObj
   $postObj = simplexml_load_string($postStr, 'SimpleXMLElement', LIBXML_NOCDATA);
  
   $fromUsername = $postObj->FromUserName; //请求消息的用户
   $toUsername = $postObj->ToUserName; //"我"的公众号id
   $keyword = trim($postObj->Content); //消息内容
   $time = time(); //时间戳
   $msgtype = 'text'; //消息类型：文本
   $textTpl = "<xml>
  <ToUserName><![CDATA[%s]]></ToUserName>
  <FromUserName><![CDATA[%s]]></FromUserName>
  <CreateTime>%s</CreateTime>
  <MsgType><![CDATA[%s]]></MsgType>
  <Content><![CDATA[%s]]></Content>
  </xml>";

  if($keyword == 'hehe'){
    $contentStr = 'hello world!!!';
    $resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgtype, $contentStr);
    echo $resultStr;
    exit();            
   }else{
    $contentStr = '输入hehe试试';
    $resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgtype, $contentStr);
    echo $resultStr;
    exit();
   }

  }else {
   echo "";
   exit;
  }
 }
 
 //验证字段
 private function checkSignature(){

  $signature = $_GET["signature"];
  $timestamp = $_GET["timestamp"];
  $nonce = $_GET["nonce"]; 
   
 $token = TOKEN;
 $tmpArr = array($token, $timestamp, $nonce);
 sort($tmpArr);
 $tmpStr = implode( $tmpArr );
 $tmpStr = sha1( $tmpStr );
 
 if( $tmpStr == $signature ){
 return true;
 }else{
 return false;
 }
 }
}

   if($postObj->MsgType == 'event'){ //如果XML信息里消息类型为event
    if($postObj->Event == 'subscribe'){ //如果是订阅事件
     $contentStr = "欢迎订阅misaka去年夏天！\n更多精彩内容：http://blog.csdn.net/misakaqunianxiatian";
     $resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgtype, $contentStr);
     echo $resultStr;
     exit();
    }
   }