I understand that this is a LAMP forum, and Ruby on Rails (RoR) may be considered off-topic, but I think this question is on the minds of most of us who are evaluating RoR vs. PHP for high-traffic Web2.0 applications. I also consider you to be highly competent and objective.
Given that things like caching, SQL tuning etc. are more important to handle high-traffic than the actual page-generation, how slow do you think RoR would be compared to PHP? Also, you talked about the performace differences between different database drivers for MySQL/PHP. Could you comment upon MySQL/RoR choices?
Thanks in advance,
First you’re comparing Language with Framework which is not exactly fair.
Framework helps you to develop stuff faster but limits your flexibility which may be very important for scaling.
There are frameworks for PHP such as CakePHP or Symphony but you would find high traffic sites such Yahoo do not use them but rather use their own stuff which is typically more lightweight and more focused on performance.
I would think about nature of your application and the goals - for many applications getting stuff done fast and working limited amount of users (with limit may be rather high) is more important than having very scalable application which takes 3 times longer to implement.