how to make multi version in codeigniter for mobile and desktop

We have a codeigniter website for desktop and we don’t want it to be responsive for desktop browsers. But we need mobile version of website in a way that be responsive for all kinds of mobiles and tablets. Also we know we need to use is_mobile function in user agent library but we don’t know where and how should we use them? And we want to use both of desktop version and mobile version in the same domain. Please kindly guide us about this problem and let us know how we can find good tutorial?

go download sprintphp from github by @kilishan I think it has feature u looking for, and based on CI3

https://github.com/ci-bonfire/Sprint