You don't think Ruby on Rails requires the overhead of a server???
There are perfectly good and very sophisticated MVC frameworks available for PHP, such as CakePHP (one of the closer to Rails, even down to the command-line "baking" of models, controllers, etc.).
There are meaningful differences to development using both languages, but criticizing PHP because it was popularized independently of any specific framework is not one of them. Especially since there are plenty of situations (think dumb but scalable web services) in which the last thing you want to do is invoke the overhead of a framework in any language.
There are perfectly good and very sophisticated MVC frameworks available for PHP, such as CakePHP (one of the closer to Rails, even down to the command-line "baking" of models, controllers, etc.).
There are meaningful differences to development using both languages, but criticizing PHP because it was popularized independently of any specific framework is not one of them. Especially since there are plenty of situations (think dumb but scalable web services) in which the last thing you want to do is invoke the overhead of a framework in any language.