I hear lots of people talking about Ruby and quite a few
job advertisements giving ROR a special mention.

Whats the big deal with Ruby vs PHP.
And should I bother to try to learn it?

I already have an intermediate knowledge of PHP/MySQL

i think you can do a lot more using less code in ruby

demand will be less than PHP but will pay more for that reason

If you are already learning PHP and MySQL, I would continue along that path until you are on an advanced level.

Although I'm hardly a RoR expert, the nice thing about it is that it allows you to rapidly deploy front-end applications. It is a framework that allows one to do AJAX and Ruby together seamlessly.