>>As Jordan mentioned, all you can do is basic validation. You'll never get the final response to see if the card is ok or not for the payment as only the bank can allow you that.
>
>You can, however, tell from teh ccno what kindof card it is, and validate that against another field. For example, if your routine determines a ccno is Visa and they specified a Mastercard, you've got problems.
>
>For simple data entry, that would be a worthwhile validation.

As Mike explain you there 3-5 differnt type of validation request and you must receive validation protokol from differnt organization if you like to have more serviced cards.
From one of our servicing organization which have friendly data services is possible to receive validation reply(ok/no) - it operate with debit cards.

Everything depend on organization and how good you are in barganing to receive as better validation protocol as possible