I'm currently using OCaml, but I would probably prefer to use Haskell. They are both far ahead of PHP.
Assuming your website is doing anything non-trivial, parallelism would certainly be useful. Just because it's a web project does not mean you're not doing something computationally intensive, after all. But even if you don't need it, it certainly doesn't hurt to have the option!
Event-driven IO allows you to maintain more connections on the same resources than a thread-based model. There is just less overhead per connection. That's going to be relevant for most web projects. If you could get this for free (that is, without having to rewrite your code like in Node.js), why wouldn't you want it?
Just because employers seek PHP does not make it a good language, or even not a bad language. It just becomes a necessary evil.
Besides, that depends entirely on the job market in your area. Where I am (near SF), PHP is not in very high demand where Java, JavaScript, Python, Ruby and Objective-C are. I've also seen jobs using Haskell, Scala and (obviously) OCaml. This is obviously going to be different elsewhere, but my point is that it's all relative and not a function of any particular language's quality.