Usually the organisation notes all its changes and updates etc. so for example if php make an update, all the details will be on the php website when it happens. So basically in that sense i would say "go to the source" :) that is one way to keep updated, if in fact you did ask "if you learn a programming language and it changes" "how do you keep yourself updated?". It's rare that a change will take place so bad that it will be like starting again, so don't panic. And that is usually in it's infancy.