PHP Culture and its user base are more attractive factors than Ruby, which is a bit Japan-centric. The barrier of human language has played an important role.

DHH is talented marketer only so I dont think RoR and Ruby can be a strong competitor to Java and PHP. Even in Japan, Ruby is reluctant alternative.

The writer of this post seems to presume that there is only one tool for every job. That's simply not true. I think that eventually Ruby (well, Rails most likely) will rise as the tool of choice in certain areas. The problem with using PHP in big projects is simply its nature. You see a lot of code clutter and ugly hacks when you have to work on existing code bases, and that's just annoying. Sure, for a script that just mails the content of a form or something like that, PHP is a good tool. Even DHH (the creator of Rails) uses PHP for such tasks, according to an interview he recently did for O'reilly (specifically, read http://www.oreillynet.com/pub/a/network/2005/08/30/ruby-rails-david-heinemeier-hansson.html?page=3).
When web applications become more complex however, I'd rather prefer a solution (read: framework) that is elegant, well documented, full featured, thoroughly tested, has a wide and helpful community and is based on popular, proven agile practices. That's the kind of applications I don't like using PHP for anymore. But it's not like you can't use these tools together. Who has ever worked in an environment where the only language being used was PHP? Besides, Ruby/Rails can well be used with Java as a backend, too (jruby.sourceforge.net). As for the complexity - I really don't agree. Ruby is not a hard language to learn. Sure, it has advanced features (blocks for example), but if you invest some time and attention into that, they're really not all that hard either. I think maybe the author of the article should give Rails a shot while keeping an open mind.