First of all, I know that feature phones aren't that popular anymore but I still want to cater for the users. What I'm asking is to be able to determine if the browser is on a feature phone instead of a smart phone. I have a stripped down version of my website that is specially for feature phone users who normally have slower internet connection.
I need to do the detection from the server side (PHP) since I want to serve them the minimal version from the get-go instead of having them load the heavy page first.