the best way to codeigniter website multi-language CMS implement

I'm researching hours and hours, but I could not find any clear, efficient way to make it :/

I have a codeigniter base website in English and I have to add a spainsh, portuguese language now. What is the best way to make my site in 3 language depending visitor selection?

all menu and footer and also content also translate when language change so which way is best for me.