title: Safest way to pass credit card number through a multi-step form?
body: <p>On step 3 I have a form which accepts a credit card, Step 4 re-prints the information including the last 4 digits of the credit card, and Step 5 I need to know the full CC # to process it and send it through my https connection to a 3rd party vendor - should I store it through hidden inputs or <code>$_SESSION</code> so I can access it in between the 3rd and 5th step?</p>
  
  <p><strong>FYI</strong>: My entire site is already https'd.</p>