I've recently started looking at Symfony. Pretty impressive really!

Be wary of Symfony if you need high performance and cannot use caching. Its runtime is not fast.

Slim is lightweight, and somewhat similar to Flask or Bottle from the Python world: https://www.slimframework.com/

You can also lighten Symfony's footprint: http://symfony.com/blog/new-in-symfony-2-8-symfony-as-a-micr...