Getting Started with Credit Cards and Session Passwords (PHP)

I just want to know if anyone can point me in the right direction - like
a good tutorial.

First, I want to add credit cards to a site. I'm not talking about
anything sophisticated, like a shopping cart system. I'm thinking of the
credit card icons you see on political candidates' websites that you
click if you want to contribute to their campaign.

Do you have to approach each credit card company and get permission,
then figure out how to make the function that collects money? Or is
there a simple script you can use that sets it up relatively easily and
plugs you into Visa, Mastercard, etc.

I also need to get started on passwords. Specifically, I need to learn
how to password-protect a page I'm going to use to add and modify
information in an online database. I think someone discussed it on this
forum a while ago and suggested "session passwords," but I can't find
that thread. It might have been another forum.

Anyway, can anyone tell me how to get started? (I'm using PHP.)

Thanks!

.oO(David B)

I also need to get started on passwords. Specifically, I need to learn
how to password-protect a page I'm going to use to add and modify
information in an online database.

The easiest way is to use basic HTTP authentication on Apache servers,
it only requires two files: a .htaccess in the directory to protect and
another file with the encrypted passwords. Then if the user requests a
file from that directory the server returns a 401 status code
("Unauthorized") and a little login box pops up in the browser. Only
little problem is that with this method it's not really possible for a
user to logout, except for closing all browser windows.

I think someone discussed it on this
forum a while ago and suggested "session passwords," but I can't find
that thread. It might have been another forum.

This would be the other way - doing it by hand with own scripts. It's
more flexible, but also a bit more complex and you have to make sure
that there are no ways to compromise the login system and directly
access the files. There are sites that check the login only on the first
page, but all following are freely accessible if you know the URL ...

HTH
Micha