There are several reasons why you may not want to rely on PHP to detect the browser. Some of them are summarized
here[
^]. In my opinion, it depends on your purpose and your target.
I am a software developer specializing in technical and numerical software systems and also a PhD Petroleum Engineer.
I started programming in IBM 1620 machine code in 1967, then FORTAN on CDC mainframes mainframes in 1970. I later used ALGOL, BASIC, FORTH, Pascal,Prolog, C, F#, C#, etc.
I generally use whatever language available thatallows me to accomplish what is neccesary.