Get a Ruby on Rails Beginner Book
I am learning Ruby on Rails right now, and I know some PHP. If you are building small to full blown apps, just get Build your own Ruby on Rails Web Applications by Patrick Lenz. I am going through this book right now, and it is an amazing introduction that will help you appreciate an elegant language! Seriously, Rails does most of the work for you!
PHP has its advantages too because as you don't have a framework in the way. If you want to learn about PHP, I would highly recommend PHP Solutions: Dynamic Web Design Made Easy (Solutions) or view the book on the publisher's site.