There is no simple answer to this question because it depends on your specific needs and preferences. RoR is known for its speed and flexibility, while PHP is known for its stability and a large community of developers.
Ultimately, the best choice for you will depend on your situation. If you need a fast, versatile development platform, RoR is probably a better choice. But if you are looking for a stable platform with a large community of support, PHP may be a better option.