I already have an express checkout integrated with my Codeigniter application. Now I want to integrate seamless paypal where I collect the CC information and pass it to Paypal (via backend) and once everything is approved, my application shows that to the user. All this with out ever going to Paypal's website.

I know that Paypal gives a bunch of sample code but they have so many different products that advertise to do the same thing.

Is there any wrapper library in PHP that I can use for handling all this?

What sort of design decision is involved in migrating to such system? Would I need SSL certificates for this?