I'm not sure if you're serious, but there are plenty of frameworks on a par with Rails at least (nb: I have zero experience with Django).
At the enterprise level, there's Symfony or Zend:
If Rails is your thing, CakePHP shares some concepts (although I'll be the first to admit CakePHP has many flaws):
Want something lightweight that's easy to jump into? CodeIgniter's the one for you!
And finally, my favourite, Kohana. Absolutely infuriating since they essentially stopped writing documentation for new versions, but if I need to get something written quickly and reliably, this is my go-to call:
There are tonnes of "serious" frameworks for PHP (I've certainly missed out a few), and frankly, if you're going to try to attack PHP, this is the wrong angle from which to do so.
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.
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.
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.
> 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.
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.
Also, the next version is supposed to redo the ORM to return actual models.
I think you meant the comparison as insulting, but it actually isn't. You're saying PHP is a T-Rex of web development. It's a nice compliment :)
Drupal is an odd duck - it's a framework with a built in CMS. It's immensely powerful for many developers who put the time in to learn it, but the experience is often jarring for traditional "object oriented" developers so they come away with a bad taste in their mouth: "no objects? this is icky!"
Of all the major PHP projects, Drupal seems to be the one embracing good software architecture - Drupal 8 looks to be amazing. It's come a long way from the days of Drupal 5.
I can't speak for Drupal or Magento, but WordPress's codebase is a world of pain. I've written a few plugins in the past, and the WordPress code is simply hell to work with.
Magento is on a whole other level of suck. I worked on a highly customized Magento site 3 years ago, and it was the worst experience of my professional career - lousy software and client-from-hades.
The Magento folder structure is just completely insane...some of the templates are like 8 or 9 subfolders deep, and it's the huge mashed up pile of Zend Framework and homegrown MVC, none of which is well documented (Since after all, they want to push you to paid support...)
Oh, and to further cement the suck, the main database tables are in EAV form. Tons of fun to be had.