Ask HN: PHP Directory structure and code organization

I work for a company (PHP shop) where we are looking at cleaning/separating our code as we move toward PSR-0 (http://www.php-fig.org/psr/psr-0/).

We have lots of different `features` that we would like to split up and organize in a way that makes the most sense.

We want: - Highly modular. - Easily extend/implement abstract code between features. - Outside the core framework.

Any suggested reading material, advice, or feedback would be fantastic!

Thanks HN! :)

Edit: We use CodeIgniter (earlier version)