function guidv4($data = null) {
          $data = $data ?? random_bytes(16);
          assert(strlen($data) == 16);
          $data[6] = chr(ord($data[6]) & 0x0f | 0x40);
          $data[8] = chr(ord($data[8]) & 0x3f | 0x80);
          return vsprintf('%s%s-%s-%s-%s-%s%s%s', str_split(bin2hex($data), 4));
        }

        $idempotencykey = guidv4();
		$bearer_token = "TOKEN FROM OAUTH FLOW";
        $s = curl_init();
        $headers = array("accept: application/json",
                      "authorization: Bearer ".$bearer_token,
                      "idempotency-key ".$idempotencykey,
                      "content-type: application/json");

        $params = array (
          'amount' => "9900",
          'currency' => 'usd',
          'source' => $_POST['cloverToken'],
        );

        curl_setopt($s, CURLOPT_URL, 'https://scl-sandbox.dev.clover.com/v1/charges');
        curl_setopt($s, CURLOPT_POST, 1);
        curl_setopt($s, CURLOPT_HTTPHEADER, $headers);
        curl_setopt($s, CURLOPT_POSTFIELDS, $params);
        $response = curl_exec($s);
        curl_close($s);