title: Post values without hidden variables and ajax?
body: <p>I am integrating a payment gateway with my website in php. They provided key and salt values to uniquely identify me. The sample code given by them store key and salt in hidden variables. I think it is not secure. </p>
  
  <p>Now my question is, is there any way that we can pass these values to payment gateway (from mysite.com/checkout.php to paymentgateway.com page). The methods like <code>file_get_contents()</code> does work as it won't redirect to payment page.</p>