for web, PHP IMO will continue to grow and dominate over the next few years. As far as I can tell I do not see any current technology surpassing it in terms of how widespread it has become. PHP is the popular choice for many reasons, 1 for being easier to learn, 2 being open source and freely distributed, it's also very well documented and integrates alot of useful technology.
Now in terms of career, for all those same reasons competition for jobs will become tighter as more and more developers enter the stage. My company put out a job posting only the find 1 out of every 4 that called were outsourcing requests.
So the question becomes will PHP be able to feed everyone's family in the long run, that question I am unsure of. But if you want to do strickly web, if (Platform !== ".net" ) PHP > Java
Because I will say, .net does seem to be a pretty poweful tool