I use NetBeans , which works well even with Symfony 2. You do not need to install anything, just create a new PHP project from the existing Symfony folder. You will get autocomplete for classes and validation check for YAML (if you use it, of course).
For Twig, you can install this plugin , which gives you syntax highlighting and nothing more. This is enough for me. The only problem I discovered is that Twig patterns are hard to read if you are using the dark (and cool) NetBeans theme: you have to use black by default on a white background.
Eclipse Symfony2: , . ( NetBeans) - , ..