Using php to develop WeChat attention events

<?php
/**
 * wechat php test
 */

//define your token
define("TOKEN", "weixin");
$wechatObj = new wechatCallbackapiTest();
//$wechatObj->valid();
$wechatObj->responseMsg();
class wechatCallbackapiTest
{
  public function valid()
  {
    $echoStr = $_GET["echostr"];

    //valid signature , option
    if($this->checkSignature()){
      echo $echoStr;
      exit;
    }
  }

  public function responseMsg()
  {
    //get post data, May be due to the different environments
    $postStr = $GLOBALS["HTTP_RAW_POST_DATA"];

    //extract post data
    if (!empty($postStr)){

        $postObj = simplexml_load_string($postStr, &#39;SimpleXMLElement&#39;, LIBXML_NOCDATA);
        $fromUsername = $postObj->FromUserName;
        $toUsername = $postObj->ToUserName;
        $type = $postObj->MsgType;
        $customevent = $postObj->Event;
        $keyword = trim($postObj->Content);
        $time = time();
        $textTpl = "<xml>
              <ToUserName><![CDATA[%s]]></ToUserName>
              <FromUserName><![CDATA[%s]]></FromUserName>
              <CreateTime>%s</CreateTime>
              <MsgType><![CDATA[%s]]></MsgType>
              <Content><![CDATA[%s]]></Content>
              <FuncFlag>0</FuncFlag>
              </xml>";       
        if($type=="event" and $customrevent=="subscribe"){
          $contentStr = "感谢你的关注\n回复1查看联系方式\n回复2查看最新资讯\n回复3查看法律文书";
          $msgType = "text";
          $resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgType, $contentStr);
          echo $resultStr;
          }  
        if(!empty( $keyword ))
        {                
          $msgType = "text";
          if($keyword=="1"){
          $contentStr = "qiphon";}
          if($keyword=="2"){
          $contentStr = "test 。";}
          if($keyword=="3"){
          $contentStr = "test333";}         
          $resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgType, $contentStr);
          echo $resultStr;
        }else{
          echo "Input something...";
        }

    }else {
      echo "";
      exit;
    }
  }

  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;
    }
  }
}

?>