PHP

<?php
// zdex.php — requires the php-curl extension

const API_KEY  = 'zd_84444a6e...';
const SECRET   = '073CuVWk...';
const BASE_URL = 'https://api.zetariumdex.com';

function signed_request(
    string $method,
    string $path,
    array $params = [],
    ?array $body = null
): array {
    $params['timestamp'] = (int)(microtime(true) * 1000);
    ksort($params);
    $qs  = http_build_query($params);
    $sig = hash_hmac('sha256', $qs, SECRET);

    $url     = BASE_URL . $path . "?{$qs}&signature={$sig}";
    $headers = ['X-API-KEY: ' . API_KEY];
    if ($body !== null) {
        $headers[] = 'Content-Type: application/json';
    }

    $ch = curl_init($url);
    curl_setopt_array($ch, [
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_CUSTOMREQUEST  => $method,
        CURLOPT_HTTPHEADER     => $headers,
        CURLOPT_POSTFIELDS     => $body !== null ? json_encode($body) : null,
    ]);

    $raw = curl_exec($ch);
    curl_close($ch);
    return json_decode($raw, true);
}

<?php
require_once 'zdex.php';

// 1. Read futures balance
$balance = signed_request('GET', '/v2/futures/balance');
print_r($balance);

// 2. Idempotent LIMIT BUY
$clientOrderId = bin2hex(random_bytes(16));
$order = signed_request('POST', '/v2/orders', [], [
    'symbol'        => 'BTCUSDT',
    'side'          => 'BUY',
    'type'          => 'LIMIT',
    'quantity'      => '0.001',
    'price'         => '30000',
    'clientOrderId' => $clientOrderId,
]);
print_r($order);

<?php
// composer require textalk/websocket
require __DIR__ . '/vendor/autoload.php';

use WebSocket\Client;

$client = new Client('wss://api.zetariumdex.com/ws');
$client->send(json_encode([
    'action'  => 'subscribe',
    'channel' => 'ticker',
    'symbol'  => 'BTCUSDT',
]));

while (true) {
    $msg = json_decode($client->receive(), true);
    if (($msg['channel'] ?? null) === 'ticker') {
        echo "{$msg['symbol']} last={$msg['data']['lastPrice']}", PHP_EOL;
    }
}