微信开发自动回复功能，消息类型判断失败，PHP语言

<?php// wechat php   //define your token定义接口define("token", "weixin");$wechatobj = new wechatcallbackapitest();$wechatobj ->getimagemsg();//这个要调用自动回复消息！！$wechatobj->valid();class wechatcallbackapitest{//>>>>>>>>>>>>>>>>>>>>>>>>>>>>>接口验证>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>	public function valid()    {        $echostr = $_get["echostr"];        //valid signature , option        if($this->checksignature()){            header('content-type:text');//在微信样本代码上添加了如此语句，因而接口接成功        	echo $echostr;        	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;        }    }//>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>//>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>自动回复消息>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>  public function getimagemsg()//自动回复消息    {           $poststr = $globals["http_raw_post_data"];        if (!empty($poststr))        {                    libxml_disable_entity_loader(true);                $postobj = simplexml_load_string($poststr, 'simplexmlelement', libxml_nocdata);                $fromusername = $postobj->fromusername;                $tousername = $postobj->tousername;                $msgtype=$postobj->$msgtype;                $picurl=trim($postobj->picurl);                $mediaid=trim($postobj->mediaid);                $time = time();                $texttpl = "<xml>                            <tousername><![cdata[%s]]></tousername>                            <fromusername><![cdata[%s]]></fromusername>                            <createtime>%s</createtime>                            <msgtype><![cdata[%s]]></msgtype>                            <content><![cdata[%s]]></content>                            <funcflag>0</funcflag>                            </xml>";                         if(strtolower($msgtype) =="image")                {                                        if(!empty($picurl)){                           $msgtype ="text";                           $contentstr = "图片链接：".$picurl."\n";                           $contentstr =$contentstr."媒体id:".$mediaid;                        }else{                            $contentstr = "请发送图片哦";                        }                           }else{                    $msgtype ="text";                    $contentstr = "我只接收图片消息";                    }                $resultstr = sprintf($texttpl, $fromusername, $tousername, $time, $msgtype, $contentstr);                echo $resultstr;        }        else         {            echo "";            exit;        }    }     }?>