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

//define your token
define("TOKEN", "weixin");
$wechatObj = new wechatCallbackapiTest();
if (isset($_GET[‘echostr‘])) {
    $wechatObj->valid();
} else {
    $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)){
                /* libxml_disable_entity_loader is to prevent XML eXternal Entity Injection,
                   the best way is to check the validity of xml by yourself */
                libxml_disable_entity_loader(true);
                      $postObj = simplexml_load_string($postStr, ‘SimpleXMLElement‘, LIBXML_NOCDATA);
                $fromUsername = $postObj->FromUserName;
                $toUsername = $postObj->ToUserName;
                $keyword = trim($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(!empty( $keyword ))
                {
                              $msgType = "text";
                        $contentStr = "Welcome to wechat world!";
                        $resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgType, $contentStr);
                        echo $resultStr;
                }else{
                        echo "Input something...";
                }

        }else {
                echo "";
                exit;
        }
    }
                
        private function checkSignature()
        {
        // you must define TOKEN by yourself
        if (!defined("TOKEN")) {
            throw new Exception(‘TOKEN is not defined!‘);
        }
        
        $signature = $_GET["signature"];
        $timestamp = $_GET["timestamp"];
        $nonce = $_GET["nonce"];
                        
                $token = TOKEN;
                $tmpArr = array($token, $timestamp, $nonce);
        // use SORT_STRING rule
                sort($tmpArr, SORT_STRING);
                $tmpStr = implode( $tmpArr );
                $tmpStr = sha1( $tmpStr );
                
                if( $tmpStr == $signature ){
                        return true;
                }else{
                        return false;
                }
        }
}

?>