# Скопируйте код формы
  <form method="POST" action="https://paynex.ru/payment/">
  <input type="hidden" name="merchant" value="268418752">
  <input type="hidden" name="description" value="Оплата">
  <input type="hidden" name="amount" value="100">
  <input type="hidden" name="currency" value="RUB">
  <input type="hidden" name="order_id" value="47658">
  <button type="submit">Оплатить></button>
  </form>
# Английская версия формы
  <form method="POST" action="https://paynex.ru/payment/en/">
  <input type="hidden" name="merchant" value="268418752">
  <input type="hidden" name="description" value="Payment">
  <input type="hidden" name="amount" value="100">
  <input type="hidden" name="currency" value="RUB">
  <input type="hidden" name="order_id" value="47658">
  <button type="submit">Pay></button>
  </form>
                  

# Установите секретный ключ
  PAYNEX.api_key = 'sk_test_BQokikJOvBi4olfQ2'
  $shop_id = '321'2,
  $amount = number_format (100.5,2,'.','');
  $currency = 'RUB'; # или "USD", "EUR"
  $description = 'Apple Watch Series 2';
  $order_id = 42351277;
  $method_id = '.';
  $client_email = '.';
  $debug = '.'; # или "1"
  $api_key = 'BQokikJOvBi4olfQ2';
  # из настроек сайта в личном кабинете
  $signature = md5( $api_key.md5(join(':',array
 ($shop_id, $amount, $currency, $description, $order_id, $method_id, $client_email, $debug, $api_key ))));
  $language = 'ru'# или 'en'

  $params['currency_from'] = 'RUB';
  $params['shop_id'] = 42351277;
  $params['amount'] = 12.50;
  $params['debug'] = 0;
  $params['comment'] = '';
  $api_key = 'BQokikJOvBi4olfQ2'; ksort($params);
  $values = array_values ($params);
  $values[] = $api_key;
  $sign = md5(join('', $values));
  $params['sign'] = $sign;
  $url = https://api.paynex.ru/v1.0/method_name/?'
  .http_build_query($params);