You know what? Not true. Learn the language, write some programs first.
When you need to learn how to use ActionMailer to send messages, learn
it then. When it comes time to work on your program from both your
laptop and your desktop machine, then learn how SubVersion works. When
you have the coolest application in the world and you want to deploy it,
then learn that.
Don’t learn it until you need it. Sure there’s a lot there, but to
learn PHP you have to set up the webserver too, and Rails has one of
those built in, so you can jump right in and develop.
Who knows… You may not like Rails (blasphemy!) so why learn EVERYTHING
at once?
I’ve used a lot of languages and Ruby and the Rails framework was the
easiest for me to learn and the most fun I’ve had, but I took it one
step at a time.
Do the “Depot” app in the Agile book. They don’t use anything but MySQL
and WEBrick for that. 
Good luck to you!