Ask HN: What web based language should we learn nowadays?

Hey, I am currently studying applied computer science (B.Sc.). Before this I've done a school job training which was in a very similiar field, but broader and obviously not as deep. During my job training and also now at university we're getting taught about web programming. Both times with PHP as the server side scripting language. Now, the other day I've got an invite from koding.com (I've signed up for their beta when it was posted on HN a while ago) and in the feed for latest messages I found a commenter saying that PHP is old and should be abandoned.

I will have to get deeper into PHP now anyway, as I obviously want to pass the semester with a good grade, but:

Should PHP actually be replaced entirely? Also, which language would be useful to learn for the future?