Gate.io PHP API create order problem => Signature mismatch - api

Question

I'm not an expert in API development or using signed messages in PHP.
I have however tried to get the GATE.IO v4 API working in my PHP implementation but keep getting "Signature mismatch". I have followed the API documentation for CREATE ORDER available at Gate.io's website here: https://www.gate.tv/docs/developers/apiv4/#create-an-order
I have managed to get the /spot/accounts working, so I know that the key and secret are correct.
Based on the code below I seem to missing something. Probably a tiny error but those are the hardest, right?
Does anyone have any idea what could be the cause of this issue? Would really appreciate your help after having spent 8+ hours trying to get this to work.
<?php
$accessToken = ''; // Access token for OAuth/Bearer authentication
$key = "XXXXXXXXXXXXXXXXXXXXXXX";
$secret = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
$username = ''; // Username for HTTP basic authentication
$password = ''; // Password for HTTP basic authentication
$host = 'https://api.gateio.ws/api/v4'; // The host
$userAgent = 'OpenAPI-Generator/5.26.0/PHP'; // User agent of the HTTP request, set to "OpenAPI-Generator/{version}/PHP" by default
$sResourcePath = "/spot/orders";
$sMethod = "POST"; // POST or GET
$aPayload['currency_pair'] = "DOT_USDT";
$aPayload['price'] = "6.330033";
$aPayload['account'] = "spot";
$aPayload['side'] = "buy";
$aPayload['amount'] = "1";
$aPayload['time_in_force'] = "gtc";
$sBody = json_encode($aPayload);
$aQueryParams = $aPayload;
$aFullPath = parse_url($host . $sResourcePath);
$fullPath = $aFullPath['path'];
$timestamp = time();
$hashedPayload = hash("sha512", ($payload !== null) ? $payload : "");
$fmt = "%s\n%s\n%s\n%s\n%s";
$sQuery = http_build_query($aQueryParams, false);
$signatureString = sprintf($fmt, $sMethod, $fullPath, $sQuery, $hashedPayload, $timestamp);
$signature = hash_hmac("sha512", $signatureString, $secret);
$aSignHeaders = array(
"KEY" => $key,
"SIGN" => $signature,
"Timestamp" => $timestamp);
$aHeaders[] = "KEY: " . $aSignHeaders['KEY'];
$aHeaders[] = "SIGN: " . $aSignHeaders['SIGN'];
$aHeaders[] = "Timestamp: " . $aSignHeaders['Timestamp'];
$aExtraParams['sHttpHeaders'] = $aHeaders;
if ($sMethod == "POST")
{
$sParams = "?" . http_build_query($aQueryParams, false);
}
else
{
$sQuery = "";
}
$sSubmitUrl = $host . $sResourcePath . $sParams;
$sPage = CURL::doRequest($sMethod, $sSubmitUrl, $sParams, $aExtraParams);
$aPage = json_decode($sPage, true);
if ($aPage)
{
$iPage = count($aPage);
}
echo "<pre>";
print_r($aPage);
echo "</pre>";
?>

Answer 1

based on that example request, you should be doing something like this
//path & urls
$host = 'https://api.gateio.ws';
$prefix = '/api/v4';
$path = '/spot/orders';
$fullPath = "$prefix$path";
$method = 'POST';
//your API keys
$api = [
'secret' => 'xxxx'
];
// Your actual data you can easily modify
$payload = [
'currency_pair' => 'DOT_USDT',
'price' => '6.330033',
'account' => 'spot',
'side' => 'buy',
'amount' => '1',
'time_in_force' => 'gtc'
];
//Convert your data to JSON FORMAT
$jsonPayload = json_encode( $payload );
//Hash your JSON DATA
$hashJsonPayload = hash('sha512', $jsonPayload);
$timeStamp = time();
// dunno if this is required
$queryParam = '';
//Create your signature string
$signString="$method\n$fullPath\n$queryParam\n$hashJsonPayload\n$timeStamp";
//Generate the signature
$signHash = hash_hmac('sha512', $signString, $api['secret']);
// Your Actual headers
$headers = [
'Content-Type: application/json',
'Timestamp: '.$timeStamp,
'Key: '.$api['secret'],
'SIGN: '.$signHash
];
Example request using php curl
$ch = curl_init( "$host$fullPath" ); // URL to POST https://api.gateio.ws/api/v4/spot/orders
curl_setopt( $ch, CURLOPT_POSTFIELDS, $jsonPayload ); // set json payload as body here
curl_setopt( $ch, CURLOPT_HTTPHEADER, $headers ); //define header here
curl_setopt( $ch, CURLOPT_RETURNTRANSFER, true );
$result = curl_exec($ch);
curl_close($ch)
echo '<pre>', print_r($result, 1), '</pre>';