Please don't recommend CodeIgniter. I'm not normally one for swathing "x is bad" judgements, but CI is simply not in the same league as the other frameworks you mentioned.
Tell us why! With the low memory overhead, built-in cache, Active Record (+PDO support) and easy-to-understand MVC approach, I think it is the best framework for writing small to medium-sized web applications.
CI is not Zend, but nothing prevents you from using the Zend libraries with a small CI Library wrapper - I have done so many times in the past, and it works great.
CI gives you very little, and what it gives you is mostly categorically broken. The total lack of post-redirect-get and insane choices on the session data front meant I was using a custom session storage library I wrote instead of the bundled one.
We had issues where the router and loader were not playing nicely at all - we were using the 404 override option in order to do some custom routing (as the router was not flexible enough for even a very basic CMS). However because of how messy the routing code is, and how much of a hack the 404 override was (last time I checked there were several open bugs regarding this on their tracker, some over a year old and completely untouched), it completely blitzed the loaded libraries, so we had to add in more hacks to dodgily clear the cache of loaded libraries and re-run the loader in order to have them available. The only other way to do this would have been to modify the core loader to fix the bug there (but we didn't want to modify core code to make it easier to keep up to date with framework changes), or completely rewrite the router (which really needs to be done, it's a mess).
The database abstraction code is very kludgy and basically useless for anything beyond utterly, utterly basic use cases (there's a reason it's low overhead - it's low everything, including functionality!)
That's just a few of the things we ran into. By the time we went to production I estimate that out of the maybe 30% of CodeIgniter we were actually using for our project, I had re-implemented as custom libraries maybe a third of that amount just to get some sane behaviour, and work around long-standing bugs. Overall I got the feeling that the framework had no solid direction, some of the core components (most critically the loader and router) were quite obviously piles of hacks rather than having been designed and engineered, and honestly the framework was not really much more re-usable or robust than our own custom in-house one. I know it's a very common developer hubris to think you could write your own framework and do a better job, but in the case of CodeIgniter I can confidently make that claim.
On the more technical and abstract side, it's insane that it doesn't use standard PSR loading (so any other library you want to use you have to write a custom wrapper), and the guidance on making re-usable libraries / modules / packages (I can't even remember the right terminology, they use these words in strange ways) is... unclear at best. It uses globals, it's tightly coupled, everything a decent framework should categorically not be. Overall I would say that the level of technical ability on people using and contributing to CI is very low, and most people I've spoken to that think it's great haven't actually used any other framework (which is, frankly, endemic of a large portion of the PHP-using world)
Edit: Also if you care about overhead, you're not writing what I would call a small to medium sized application! Any framework out there worth its salt (and many that are not) will be able to run your application just fine, it's extremely unlikely that the PHP layer will be the bottleneck unless you're writing really terrible code or using a really terrible framework.
Please don't recommend CodeIgniter. I'm not normally one for swathing "x is bad" judgements, but CI is simply not in the same league as the other frameworks you mentioned.
I wouldn't have a few years ago, but the current version seems decent enough. Out of interest, what're your main complaints with it?
I'm not a huge fan of CI, but would prefer it to my personal bugbear, CakePHP.
Having taken over a project that uses CI at it's core, I've found a number of things that definitely put it in a league below frameworks that were built with PHP 5.3 in mind.
* Way too much magic - everything (libraries, models, etc.) is globbed onto a superglobal class, which breaks auto-complete in IDEs and in general makes debugging harder
* No proper autoloader (PSR-0 style) - the built in autoloader can't autoload anything that doesn't fit into the CI world which tends to lead to unnecessarily large classes (anything that isn't a model gets lumped into a library)
* Setting up routes gets messy fast (it's all defined as a single associative array)
* No built in template system (which, in my experience, encourages bad behavior in views)
Okay, so a bunch of personal preferences that don't actually matter in the real world? Thanks for your insight, but it does not make CodeIgniter bad.
> frameworks that were built with PHP 5.3 in mind.
Well no crap, CodeIgniter is built for newbies in mind, people who don't have up to date PHP installs because their shared hosting doesn't keep it THAT up to date.
The newest versions of CodeIgniter are VERY good, and just like the haters of PHP, you're just hating on versions of CodeIgniter that are at least 3 versions old. Learn the updated system, then base your claims on that, not something you looked at 2+ years ago.
Those aren't (all) personal preferences. Using superglobals is definitively bad, in the same way that using GOTO is. Not using PSR-0 autoloading is flying in the face of the community consensus and makes it much harder to use other libraries with CI compared to other frameworks.
Your point about PHP versions isn't very valid. 5.3 is over 3 years old now! Plenty of cheap hosts are far more up to date than that.
There is a difference between being "newbie friendly" (which I will admit, CI is - it's a lot easier to get into than say, Zend, by orders of magnitude) and "enabling bad practices". You could say that using mysqli and concatenating data into your queries is newbie friendly, and it is - it's a lot simpler conceptually than prepared statements, but that doesn't stop it being categorically a bad idea.
For the record my CI experience ended about 9 months ago, and I have contributed code to CI, so I feel that when I say certain parts of the internals are very badly coded I do have some valid perspective on that issue.
CI is not Zend, but nothing prevents you from using the Zend libraries with a small CI Library wrapper - I have done so many times in the past, and it works great.