Why does the title mention Ubuntu? It's interesting to see how people now associate Linux with Ubuntu. And that's a good thing. It means that the desktop revolution is on it's way!
1. Based on content management: PHP. The biggest publishing site on the Web, Wordpress, uses it.
2. Based on libraries: PHP. You have PECL, PEAR, ezComponent, Zend and many others. Whatever you need, it has it.
3. Based on syntax: PHP. It's damn simple.
4. Based on deployment: PHP. It's fast and painless.
5. Based on execution model. PHP. mod_php, as an apache module, works and it’s scalable.
6. Based on frameworks: PHP. Symfony and Zend Framework offer a modular, MVC, loosely-couple architecture. They not only provide a solid infrastructure, but also an extensive component library.
7. Based on performance: Any, as long as you cache everything.