cURL request

$post = [
        'offer.id' => $offerID,
        'subscriber.name' => $first_name,
        'subscriber.surname' => $last_name,
        'subscriber.email' => "",
        'subscriber.phoneNumber' => $phone,
        'privacyPolicyUrl' => true,
        'paymentType' => 'CC',
        'paymentCard.cardHolderName' => $cardholder_name,
        'paymentCard.cardNumber' => $card_number,
        'paymentCard.expireMonth' => $card_month,
        'paymentCard.expireYear' => $card_year,
        'paymentCard.cvc' => $card_cvc,
        'companySiteName' => $options['site_name'],
        'callbackUrl' => $options['callback_url']
    ];

    $post_send = http_build_query($post, '', '&');

    $headers = [];

    $ch = curl_init('https://sandbox.subscreasy.com/na/subscription/start/4ds');
    curl_setopt($ch, CURLOPT_HTTPHEADER, array(
        'Content-Type: application/x-www-form-urlencoded'
    ));
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $post_send);
    curl_setopt($ch, CURLOPT_VERBOSE, true);
    curl_setopt($ch, CURLOPT_HEADER, 1);



// this function is called by curl for each header received
    curl_setopt($ch, CURLOPT_HEADERFUNCTION,
        function($curl, $header) use (&$headers)
        {
            $len = strlen($header);
            $header = explode(':', $header, 2);
            if (count($header) < 2) // ignore invalid headers
                return $len;

            $name = strtolower(trim($header[0]));
            if (!array_key_exists($name, $headers))
                $headers[$name] = [trim($header[1])];
            else
                $headers[$name][] = trim($header[1]);

            return $len;
        }
    );

    $response = curl_exec($ch);

    print_r($headers);

    curl_close($ch);