问调用接口签名错误，请大神帮忙看一下，万分感谢！？

代码如下：

$time=time();

$nonce=rand();

$secretId = "AKIDZEm5IR1lCXnemqsaGtQp6WTChx0psjHb";

$secretKey = "GG1YqujkPRFtKYWLdi9LJ4bss9D2cy71";

$param["Nonce"] = $nonce;

$param["Timestamp"] = $time;

$param["SecretId"] = $secretId;

$param["Action"] = "SearchMedia";

$param["Version"] = "2018-07-17";

ksort($param);

$signStr = "GETvod.tencentcloudapi.com/?";

foreach ( $param as $key => $value ) {

$signStr = $signStr . $key . "=" . $value . "&";

}

$signStr = substr($signStr, 0, -1);

$signature = base64_encode(hash_hmac("sha1", $signStr, $secretKey, true));

$param["Signature"]=urlencode($signature);

$result=$this->postData('https://vod.tencentcloudapi.com/',$param);

postData代码如下：

function postData($url,$data,$header=array()) {

$ch = curl_init();

curl_setopt($ch, CURLOPT_TIMEOUT, 3600);

curl_setopt($ch, CURLOPT_URL, $url);

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER,FALSE);

curl_setopt($ch, CURLOPT_SSL_VERIFYHOST,FALSE);

curl_setopt($ch, CURLOPT_HEADER, FALSE);

curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);

curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_0);

if (count($header)) {

curl_setopt($ch, CURLINFO_HEADER_OUT, true);

curl_setopt($ch, CURLOPT_HTTPHEADER, $header);

}

if (is_array($data)) {

curl_setopt($ch, CURLOPT_POST, 1);

if(count($data)) {

curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($data));

}else{

curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data,JSON_FORCE_OBJECT));

}

}

$res = curl_exec($ch);

// print_r(json_encode(curl_getinfo($ch)));die();

curl_close($ch);

return $res;

}

始终返回{"Response":{"Error":{"Code":"AuthFailure.SignatureFailure","Message":"The provided credentials could not be validated. Please check your signature is correct."},"RequestId":"a80355e8-ea69-465f-a3c4-b2ed46e1b757"}}

必传参数都传了啊，请问到底是什么地方错了呢，请大神帮忙一下，非常感谢！