I've done a lot of googling around this, and practically all of the answers I find are pre 2011, and are answered in the usual, here are the 5 most popular frameworks... So I'd like to update this topic for 2012,

I'm going to build a web application with a pretty complex back-end system driving it, and I'd like to use a framework so I don't have to reinvent the wheel. My application will be hugely user based, so I would appreciate a built in authentication/validation system. (When this is missing it takes me a good 2 weeks of intense and frivolous research to try to pick the "best" one (I don't want to roll my own, I don't think I'd do a better job than what's out there). I've looked into a tried a few, so I'll give you what I like and don't like, but I don't want to bias answers too much.

I don't like:

• Frameworks that auto-generate bloated code. If they have the feature, fine, but if I have to use it, I get frustrated.
• Backwards compatibility with php4, eww. I don't need backwards compatibility at all.

I like:

• Getting up and running quickly (but without all the auto-generation bogus), what I mean by this is that all the essentials are there, so I don't have to come to a grinding halt to research what the best 3rd party plugin is to get the feature I need.
• Thorough documentation, good tutorials. Good presentation of these materials.

Please explain why your framework suggestion is good, don't just give the name of a framework without any justification. Thanks!