PHP vs Ruby On Rails

I wanted to know the main advantages of using Ruby on Rails over PHP. The main hurdle that I foresee is the initial installation and configuration of RoR. I have been using PHP for over two years now and it's AMP stack installation (in my case MAMP on mac and also XAMPP and WAMP) are so much easy to install and use. I have seen many videos on RoR installation and configuration and to be honest with you it really seem quite a bit of work. I had come across the Rails installer but unfortunately it is not advised to install this on MAC OSX. This kind of makes the installation of this stack quite off putting especially as one could have a PHP app started and under way in next to no time without the headache of manual configuration. Any help or advice on this area of interest would be very much appreciated.