I'm using an ajax registration form plugin for my website and I'm thinking to implement also Paypal.

Here is how I want to implement it :

I have 3 labels ( Name, Phone, Email, ) and a " Buy " button.

After the user is typing his name, phone and email they click on "Buy" and they will be redirected to the paypal payment page or if it's possible to stay on the same page.

Probably, what I need to know is how to make the "Buy " only after the forms ( name, phone, email ) are validated.

Is there a plugin, or a snippet of code already made to not start something which already exists.