Because PHP is a framework disguised as a language.
heh. It does if he wants to later complain about html and php code all mixed up.
The only reason that is true is that he chose not to use a micro framework for php.
That's fair, I took that particular whinge out.
You could have investigated micro php framework like silex tbh (silex.sensiolabs.org), with which you could have used Twig template (twig.sensiolabs.org). A bit an overkill for such a trivial task, though.
Will Passenger just serve up ERB files just like PHP? Now I'm curious.
You don't need Passenger. Just write the sinatra app, then 'ruby <yourapp>.rb'.
He isn't talking about the sinatra example. He is talking about apache/passenger serving .erb files directly as apache/mod_php does for .php files.
I don't think it can(I did a quick search to confirm). But with apache, you can install a ruby script as cgi which renders the erbs and returns them.