关于微信开发模式的PHP代码,该怎么解决

/**
  * 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, 'SimpleXMLElement', LIBXML_NOCDATA);
                $fromUsername = $postObj->FromUserName;
                $toUsername = $postObj->ToUserName;
				$type =$postObj->MsgType;
				$customevent = $postObj->Event;
				$latitude =$postObj->Location_X;
				$longitude =$postObj->Location_Y;
                $keyword = trim($postObj->Content);
                $time = time();
                $textTpl = "
							
							
							%s
							
							
							0
							";             
			switch($type)
			{
			case "event";
			if($customevent == "subscribe")
			{$contentStr = "感谢关注"}
			break;
			case "image"
			$contentStr ="图片很棒"；
		    break;
			case "location";
			$contentStr ="{$latitude},{longitude}";
			break;
			case "text";
			switch($keyword)
			{case "1"
			 $contentStr="1"
			 break;
			 case "2"
			 $contentStr ="2"
			 break;
			 default;
			 $contentStr= "hi";}
			 break;
			 }
			 $msgType = "text";
			 $resultStr = sprintf($textTpl,$fromUsername,$toUsername,$time,$msgType,$contentStr);
			 echo $resultStr;
			 }else             	
              {
        	echo "";
        	exit;
        }
    }
		
	private function checkSignature()
	{
        $signature = $_GET["signature"];
        $timestamp = $_GET["timestamp"];
        $nonce = $_GET["nonce"];	
        		
		$token = TOKEN;
		$tmpArr = array($token, $timestamp, $nonce);
		sort($tmpArr, SORT_STRING);
		$tmpStr = implode( $tmpArr );
		$tmpStr = sha1( $tmpStr );
		
		if( $tmpStr == $signature ){
			return true;
		}else{
			return false;
		}
	}
}

?>

public function valid()
    {
        $echoStr = $_GET["echostr"];
 
        //valid signature , option
        if($this->checkSignature()){
            echo $echoStr;
            exit;
        }
    }

public function valid()
    {