问{"code":-81,"message":"签名为空"}？

查询目录/视频属性信息：调用接口：web.video.myqcloud.com/files/v1/appid/bucket_name/DirName/filename<?php$appid = "10014648";$bucket = "12yyyy";$secret_id = "AKIDL8YoyhNttAohkGMXUtKDnpsL1isRnJP6";$secret_key = "hV4wevgvhyqQR2yaStnbVmBDz1Zsg4zF";$expired = time() + 6000;$current = time();$rdm = rand();$srcStr = 'a='.$appid.'&b='.$bucket.'&k='.$secret_id.'&e='.$expired.'&t='.$current.'&r='.$rdm.'&f=';$signStr = base64_encode(hash_hmac('SHA1', $srcStr, $secret_key, true).$srcStr);$url = "http://web.video.myqcloud.com/files/v1/10014648/12yyyy/5670d0761bdf6.mp4?op=stat&Authorization=".$signStr;echo $url; //初始化 $curl = curl_init(); //设置抓取的url curl_setopt($curl, CURLOPT_URL, $url); //设置头文件的信息作为数据流输出 curl_setopt($curl, CURLOPT_HEADER, 1); //设置获取的信息以文件流的形式返回，而不是直接输出。 curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1); //执行命令 $data = curl_exec($curl); //关闭URL请求 curl_close($curl); //显示获得的数据 print_r($data);?>------------------------------------------------------------------------------------------------------结果：{"code":-81,"message":"签名为空"}