tp5+微信公众号服务器配置时使用官方sdk还是token验证失败

    public function callback()
    {

        $signature = $_GET["signature"];
        $timestamp = $_GET["timestamp"];
        $nonce = $_GET["nonce"];
        $echostr = $_GET['echostr'];
        $token = 'khePcWQZudjwbvnKBoJbZfWrHjnw';
        $tmpArr = array($token, $timestamp, $nonce);
        sort($tmpArr, SORT_STRING);
        $tmpStr = implode( $tmpArr );
        $tmpStr = sha1( $tmpStr );
        header('content-type:text');//新增
        if( $tmpStr == $signature ){
            ob_clean();//新增
            echo $echostr;
        }else{
            return 123123;
        }
    }