I've been researching for a good way to get the devicetype to trigger mobile websites and many people still use script that gets the screen width/height in pixels to determine if mobile devices are used or not.
But mobile phones/tablets have extremely high resolution screens so we need to get another way to trigger a switch between normal websites and mobile websites. Screen sizes are around 1,280 x 768 - 1920x1080 for mobile phones and 1920x1080 to 2560x1600 for tablets.
What is the correct error-proof method to determine mobile or not? I'd like not to use javascript over php, if there's an easier method then javascript please tell!