The way I see it if you have a web game everything is done client-sidedly unless it's a multiplayer game in which case some server sided stuff is needed for synching and preventing cheating.
well, if it's a web game, then you gotta have a server. I guess you could still make it without using any server-sided scripting, but I mean, you've already got a server, so why not add some server-sided functionality, like high scores or statistics or whatever
You can't make a simple text game with just JS or PHP?
well, PHP is server-sided
but yeah, you probably could just make it in JS alone. what kinda game are you talking about though? like a choose-your-own adventure kinda thing? or what? cus knowing the specifics of what you'll need depends on knowing that