CanonicalRequest =
    HTTPRequestMethod + '\\n' +
    CanonicalURI + '\\n' +
    CanonicalQueryString + '\\n' +
    CanonicalHeaders + '\\n' +
    SignedHeaders + '\\n' +
    HashedRequestPayload

POST
/

content-type:application/json; charset=utf-8
host:cvm.tencentcloudapi.com

content-type;host
35e9c5b0e3ae67532d3c9f17ead6c90222632e5b1ff7f6e89887f1398934f064

StringToSign =
    Algorithm + \\n +
    RequestTimestamp + \\n +
    CredentialScope + \\n +
    HashedCanonicalRequest

TC3-HMAC-SHA256
1551113065
2019-02-25/cvm/tc3_request
5ffe6a04c0664d6b969fab9a13bdab201d63ee709638e2749d62a09ca18d7031

$secretDate = hash_hmac("SHA256", $date, "TC3".$secretKey, true);
$secretService = hash_hmac("SHA256", $service, $secretDate, true);
$secretSigning = hash_hmac("SHA256", "tc3_request", $secretService, true);
$signature = hash_hmac("SHA256", $stringToSign, $secretSigning);
echo $signature.PHP_EOL;

$authorization = $algorithm
    ." Credential=".$secretId."/".$credentialScope
    .", SignedHeaders=content-type;host, Signature=".$signature;
echo $authorization.PHP_EOL;

TC3-HMAC-SHA256 Credential=AKIDz8krbsJ5**********mLPx3EXAMPLE/2019-02-25/cvm/tc3_request, SignedHeaders=content-type;host, Signature=72e494ea8******************************************a96525168

POST https://cvm.tencentcloudapi.com/
Authorization: TC3-HMAC-SHA256 Credential=AKIDz8krbsJ5**********mLPx3EXAMPLE/2019-02-25/cvm/tc3_request, SignedHeaders=content-type;host, Signature=72e494ea8******************************************a96525168
Content-Type: application/json; charset=utf-8
Host: cvm.tencentcloudapi.com
X-TC-Action: DescribeInstances
X-TC-Version: 2017-03-12
X-TC-Timestamp: 1551113065
X-TC-Region: ap-guangzhou

{"Limit": 1, "Filters": [{"Values": ["\\u672a\\u547d\\u540d"], "Name": "instance-name"}]}

<?php
$secretId = "AKIDz8krbsJ5**********mLPx3EXAMPLE";
$secretKey = "Gu5t9xGAR***********EXAMPLE";
$host = "cvm.tencentcloudapi.com";
$service = "cvm";
$version = "2017-03-12";
$action = "DescribeInstances";
$region = "ap-guangzhou";
// $timestamp = time();
$timestamp = 1551113065;
$algorithm = "TC3-HMAC-SHA256";

// step 1: build canonical request string
$httpRequestMethod = "POST";
$canonicalUri = "/";
$canonicalQueryString = "";
$canonicalHeaders = "content-type:application/json; charset=utf-8\\n"."host:".$host."\\n";
$signedHeaders = "content-type;host";
$payload = '{"Limit": 1, "Filters": [{"Values": ["\\u672a\\u547d\\u540d"], "Name": "instance-name"}]}';
$hashedRequestPayload = hash("SHA256", $payload);
$canonicalRequest = $httpRequestMethod."\\n"
    .$canonicalUri."\\n"
    .$canonicalQueryString."\\n"
    .$canonicalHeaders."\\n"
    .$signedHeaders."\\n"
    .$hashedRequestPayload;
echo $canonicalRequest.PHP_EOL;

// step 2: build string to sign
$date = gmdate("Y-m-d", $timestamp);
$credentialScope = $date."/".$service."/tc3_request";
$hashedCanonicalRequest = hash("SHA256", $canonicalRequest);
$stringToSign = $algorithm."\\n"
    .$timestamp."\\n"
    .$credentialScope."\\n"
    .$hashedCanonicalRequest;
echo $stringToSign.PHP_EOL;

// step 3: sign string
$secretDate = hash_hmac("SHA256", $date, "TC3".$secretKey, true);
$secretService = hash_hmac("SHA256", $service, $secretDate, true);
$secretSigning = hash_hmac("SHA256", "tc3_request", $secretService, true);
$signature = hash_hmac("SHA256", $stringToSign, $secretSigning);
echo $signature.PHP_EOL;

// step 4: build authorization
$authorization = $algorithm
    ." Credential=".$secretId."/".$credentialScope
    .", SignedHeaders=content-type;host, Signature=".$signature;
echo $authorization.PHP_EOL;

$curl = "curl -X POST https://".$host
    .' -H "Authorization: '.$authorization.'"'
    .' -H "Content-Type: application/json; charset=utf-8"'
    .' -H "Host: '.$host.'"'
    .' -H "X-TC-Action: '.$action.'"'
    .' -H "X-TC-Timestamp: '.$timestamp.'"'
    .' -H "X-TC-Version: '.$version.'"'
    .' -H "X-TC-Region: '.$region.'"'
    ." -d '".$payload."'";
echo $curl.PHP_EOL;

{
    'Action' : 'DescribeInstances',
    'InstanceIds.0' : 'ins-09dx96dg',
    'Limit' : 20,
    'Nonce' : 11886,  
    'Offset' : 0,
    'Region' : 'ap-guangzhou',
    'SecretId' : 'AKIDz8krbsJ5**********mLPx3EXAMPLE',
    'Timestamp' : 1465185768,
    'Version': '2017-03-12',
}

Action=DescribeInstances&InstanceIds.0=ins-09dx96dg&Limit=20&Nonce=11886&Offset=0&Region=ap-guangzhou&SecretId=AKIDz8krbsJ5**********mLPx3EXAMPLE&Timestamp=1465185768&Version=2017-03-12

GETcvm.tencentcloudapi.com/?Action=DescribeInstances&InstanceIds.0=ins-09dx96dg&Limit=20&Nonce=11886&Offset=0&Region=ap-guangzhou&SecretId=AKIDz8krbsJ5**********mLPx3EXAMPLE&Timestamp=1465185768&Version=2017-03-12

$secretKey = 'Gu5t9xGAR***********EXAMPLE';
$srcStr = 'GETcvm.tencentcloudapi.com/?Action=DescribeInstances&InstanceIds.0=ins-09dx96dg&Limit=20&Nonce=11886&Offset=0&Region=ap-guangzhou&SecretId=AKIDz8krbsJ5**********mLPx3EXAMPLE&Timestamp=1465185768&Version=2017-03-12';
$signStr = base64_encode(hash_hmac('sha1', $srcStr, $secretKey, true));
echo $signStr;

EliP9YW3pW28FpsEdkXt/+WcGeI=

# 実際の呼び出し、成功した場合、消費型APIであれば課金が発生する可能性があります（ここではPython言語を例としてgetリクエストを送信します）
resp = requests.get("https://" + endpoint, params=data)
# 送信リクエスト文字列の出力
print(resp.url)

最終的に得られるリクエスト文字列は
https://cvm.tencentcloudapi.com/?Action=DescribeInstances&InstanceIds.0=ins-09dx96dg&Limit=20&Nonce=11886&Offset=0&Region=ap-guangzhou&SecretId=AKIDz8krbsJ5**********mLPx3EXAMPLE&Signature=EliP***********************eI%3D&Timestamp=1465185768&Version=2017-03-12

<?php
$secretId = "AKIDz8krbsJ5**********mLPx3EXAMPLE";
$secretKey = "Gu5t9xGAR***********EXAMPLE";
$param["Nonce"] = 11886;//rand();
$param["Timestamp"] = 1465185768;//time();
$param["Region"] = "ap-guangzhou";
$param["SecretId"] = $secretId;
$param["Version"] = "2017-03-12";
$param["Action"] = "DescribeInstances";
$param["InstanceIds.0"] = "ins-09dx96dg";
$param["Limit"] = 20;
$param["Offset"] = 0;

ksort($param);

$signStr = "GETcvm.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));
echo $signature.PHP_EOL;
// need to install and enable curl extension in php.ini
// $param["Signature"] = $signature;
// $url = "https://cvm.tencentcloudapi.com/?".http_build_query($param);
// echo $url.PHP_EOL;
// $ch = curl_init();
// curl_setopt($ch, CURLOPT_URL, $url);
// $output = curl_exec($ch);
// curl_close($ch);
// echo json_decode($output);

{
    "Response": {
        "TotalCount": 0,
        "InstanceStatusSet": [],
        "RequestId": "b5b41468-520d-4192-b42f-595cc34b6c1c"
    }
}

{
    "Response": {
        "Error": {
            "Code": "AuthFailure.SignatureFailure",
            "Message": "The provided credentials could not be validated. Please check your signature is correct."
        },
        "RequestId": "ed93f3cb-f35e-473f-b9f3-0d451b8b79c6"
    }
}