Regex for names with special characters (Unicode)

Question

Okay, I have read about regex all day now, and still don't understand it properly. What i'm trying to do is validate a name, but the functions i can find for this on the internet only use [a-zA-Z], leaving characters out that i need to accept to.

I basically need a regex that checks that the name is at least two words, and that it does not contain numbers or special characters like !"#¤%&/()=..., however the words can contain characters like æ, é, Â and so on...

An example of an accepted name would be: "John Elkjærd" or "André Svenson"
An non-accepted name would be: "Hans", "H4nn3 Andersen" or "Martin Henriksen!"

If it matters i use the javascript .match() function client side and want to use php's preg_replace() only "in negative" server side. (removing non-matching characters).

Any help would be much appreciated.

Update:
Okay, thanks to Alix Axel's answer i have the important part down, the server side one.

But as the page from LightWing's answer suggests, i'm unable to find anything about unicode support for javascript, so i ended up with half a solution for the client side, just checking for at least two words and minimum 5 characters like this:

if(name.match(/\S+/g).length >= minWords && name.length >= 5) {
  //valid
}

An alternative would be to specify all the unicode characters as suggested in shifty's answer, which i might end up doing something like, along with the solution above, but it is a bit unpractical though.