integrate stripe API

The library itself are using cURL, you don't need to use CodeIgniter's own CURLRequest class. You can however do that if you like, but that means you need to implement everything they have already done.

You don't need to create a library, but if you are going to use it in multiple Controllers, you should do it. Every time you come across a function or group of functions you are using multiple times, move them to a library.

https://stripe.com/docs/development