I use PHP an Python. Not exactly Rails, but it's a similar question.<p>They both have their place, and they both have situations where one is an easier/better choice than the other.<p>Pick the best tools for the job. It doesn't matter how awesome your power drill is, even a double-clawed hammer is better at driving in nails.
I mastered PHP, Python, JavaScript, Java. For me the only reason to use PHP is availability on every low cost host. I don't found any other arguments to use PHP.
PHP has a much larger install base on commercial web hosts than Ruby, so I would consider it a perfect tool for a self-hosted application.<p>Also keep in mind PHP5 is not the same relic of the past that people constantly bitch about.