一、简介

微信公众平台可以根据用户发送的信息进行判断，然后给出对应的回复，具有良好的交互性。下文将模拟简单的回复功能，根据这个案例，开发者也可以基本理解微信交互的原理，进行更深层次的开发。

二、思路分析

用户发送过来的文本信息，我们可以提取关键字，通过简单的 if...elseif...else... 实现。

关键代码如下：

if($keyword=="你好"){
　　$contentStr = "hello";
}elseif($keyword=="苏州"){
　　$contentStr = "上有天堂，下有苏杭";
}else{
　　$contentStr = "感谢您关注【卓锦苏州】 微信号：zhuojinsz";
}

如果用户发送"你好"，则回复"hello"，如果用户发送"苏州"，则回复"上有天堂，下有苏杭"，其他信息，则回复你的欢迎词。

三、完整代码

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

//define your token
define("TOKEN", "zhuojin");
$wechatObj = new wechatCallbackapiTest();
$wechatObj->responseMsg();
//$wechatObj->valid();

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, 'SimpleXMLElement', LIBXML_NOCDATA);
                $RX_TYPE = trim($postObj->MsgType);

                switch($RX_TYPE)
                {
                    case "text":
                        $resultStr = $this->handleText($postObj);
                        break;
                    case "event":
                        $resultStr = $this->handleEvent($postObj);
                        break;
                    default:
                        $resultStr = "Unknow msg type: ".$RX_TYPE;
                        break;
                }
                echo $resultStr;
        }else {
            echo "";
            exit;
        }
    }

    public function handleText($postObj)
    {
        $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";

            if($keyword=="你好"){
                $contentStr = "hello";
            }elseif($keyword=="苏州"){
                $contentStr = "上有天堂，下有苏杭";
            }else{
                $contentStr = "感谢您关注【卓锦苏州】 微信号：zhuojinsz";
            }
            $resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgType, $contentStr);
            echo $resultStr;
        }else{
            echo "Input something...";
        }
    }

    public function handleEvent($object)
    {
        $contentStr = "";
        switch ($object->Event)
        {
            case "subscribe":
                $contentStr = "感谢您关注【卓锦苏州】"."\n"."微信号：zhuojinsz"."\n"."卓越锦绣，名城苏州，我们为您提供苏州本地生活指南，苏州相关信息查询，做最好的苏州微信平台。"."\n"."目前平台功能如下："."\n"."【1】 查天气，如输入：苏州天气"."\n"."【2】 查公交，如输入：苏州公交178"."\n"."【3】 翻译，如输入：翻译I love you"."\n"."【4】 苏州信息查询，如输入：苏州观前街"."\n"."更多内容，敬请期待...";
                break;
            default :
                $contentStr = "Unknow Event: ".$object->Event;
                break;
        }
        $resultStr = $this->responseText($object, $contentStr);
        return $resultStr;
    }
    
    public function responseText($object, $content, $flag=0)
    {
        $textTpl = "<xml>
                    <ToUserName><![CDATA[%s]]></ToUserName>
                    <FromUserName><![CDATA[%s]]></FromUserName>
                    <CreateTime>%s</CreateTime>
                    <MsgType><![CDATA[text]]></MsgType>
                    <Content><![CDATA[%s]]></Content>
                    <FuncFlag>%d</FuncFlag>
                    </xml>";
        $resultStr = sprintf($textTpl, $object->FromUserName, $object->ToUserName, time(), $content, $flag);
        return $resultStr;
    }


    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;
        }
    }
}

?>

四、测试