RIA calling

i have been reading and talking to a few ppl recently about Web2.0 trends and upcoming technologies, and RIA has been one hot topic in all of my findings..

Well its not that i have got to know about this for the first time ever.. i have been playing around with a lot of RIA tools on the net but now I'm getting attracted to build a few apps on my own..

I feel that this would be good for my personal and professional growth as well.. as a .net developer, the best option looks like learning FLEX and get of the bandwagon this way.. but i am still unsure if i should be learning PHP too.. i mean, its not essential for RIA or Web2.0 but still its one of the favorites with the developers..

I'm considering my options .. lets see what i get on with..