Instead of focusing on making a PHP framework that's like Rails, you should focus on "how can I boost developers' productivity in a unique way?" This is how libraries and frameworks become popular. If you try to model your software after existing software, it'll only ever be second-best, at best. Rails became popular despite few people knowing Ruby because it took full advantage of the language's expressiveness and e…
Look to Zend Framework 2, Symfony2, Silex, hell even Laravel 4 for quality products.