Signed OKEX requests with CURL and PHP

okex.php

$time   = round(microtime(true), 3);
$method = strtoupper($method);
$string = $time . $method . $endpoint;
$hash   = hash_hmac('sha256', $string, $secret);
$hash   = base64_encode(hex2bin($hash));

$curl = curl_init();

curl_setopt_array($curl, array(
	CURLOPT_URL            => 'https://www.okex.com' . $endpoint,
	CURLOPT_RETURNTRANSFER => true,
	CURLOPT_TIMEOUT        => 10,
	CURLOPT_CUSTOMREQUEST  => $method,
	CURLOPT_HTTPHEADER     => array(
		"OK-ACCESS-KEY: " . $apiKey,
		"OK-ACCESS-SIGN: $hash",
		"OK-ACCESS-TIMESTAMP: $time",
		"OK-ACCESS-PASSPHRASE: " . $passphrase
	)
));

$result = curl_exec($curl);