Whats the market for ruby & rails?

as it is a new technology,whats the scope of market of this technology?

Neither Ruby nor Rails is really new (in “Internet years”).
But there does appear to be a renewed interest in Ruby-on-Rails recently.

I am not qualified to answer such a question but, also, I think the question needs a bit of clarification. In what sense do you mean “Market”? As far as marketability of a developer with skills/experience in the technology?
The technology itself is Open Source so it is not ‘marketed’.

If you’re asking about the number of jobs available try searching the popular job boards for your area.
Personally, this secondary. Rails is the best way I know how to build web applications, that is the reason I use it.

Can ruby and rail is fast than PHP ,

No, people don’t choose Rails because it’s fast.
PHP isn’t a framework, so only you can make it slow.

Rails does a heck of a lot for you and this comes at a cost, but it’s well worth it in my opinion.