问signature 4100 身份认证错误 为啥？

php代码   大佬帮我看下哪里写错了
/**
 * 腾讯云鉴权
 */
private function get_signature($code){
    $secretKey = '***************';
    $secretid = "**************";
    $action = "GetUserAccessToken";
    $nonce = rand(100000,999999);
    $timestamp = time();
    $srcStr = 'GETopen.api.qcloud.com/v2/index.php?Action='.$action.'&Nonce='.$nonce.'&SecretId='.$secretid.'&SignatureMethod=HmacSHA256&Timestamp='.$timestamp.'&userAuthCode='.$code;
    $signStr = base64_encode(hash_hmac('sha256', $srcStr, $secretKey, true));
    $signStrs = urlencode($signStr);
    return $signStrs;
}