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Notes on Choosing a PHP Framework: A Quick Comparison of CodeIgniter and Kohana
February 23rd, 2008

When I was reading through my subscribed feeds I came across this post: Notes on Choosing a PHP Framework: A Comparison of CakePHP and the Zend Framework by Chad Kieffer.

Chad has done a great job comparing the two frameworks that he’s interested in. That inspired me to write something up for the frameworks that I prefer and use. :)

I began hunting for PHP frameworks ever since Ruby on Rails hit the street. Coincidentally one of the first PHP frameworks I played with was CakePHP. At that time CakePHP’s documentation was nearly non-existent so I had to seek for an alternative. I did a lot of searches, and researches, and finally I was happy to see CodeIgniter. Its user guide was what impressed me the most, I am sure many of the fellow CI users would agree with me on this one. Because of the excellent documentation, I was able to start working on projects right after I spent a few hours on the user guide! Developing apps on CI was such a breeze! Today, I develop web applications in CodeIgniter, Kohana and Zend Framework. If you want to find out how to use Zend Framework components with CI or Kohana, please read my previous blog entry: Using Zend Framework with CodeIgniter.

From version 1.2 when I first started coding on CI, to the newly released version 1.6.1 it sure is a long way. CodeIgniter has progressed well and gained many web developers’ trust, despite a few glitches. One of which was the spawn of the fork: Kohana.

CodeIgniter had some low periods where developers were all focused on pushing out new releases of ExpressionEngine, their commercial blogging/cms product. Some of the users on the CI forum got frustrated because their bug reports and feature requests were ignored. As a result of that, BlueFlame was born, and later renamed to Kohana.

Kohana is relatively unknown to the public. In fact, most of the Kohana users are ex-CI users or users that uses both CI and Kohana (like myself). According to the Kohana homepage and Wikipedia, the differences between Kohana and CodeIgniter are:

1. Strict PHP5 OOP. Offers many benefits: visibility protection, automatic class loading, overloading, interfaces, abstracts, and singletons.
2. Kohana has joined the GoPHP5 initiative. All releases from 2.2 on will conform with this project.
3. Continues CodeIgniter design patterns. Anyone who has used CodeIgniter will quickly understand Kohana’s structure and design patterns.
4. Community, not company, driven. Kohana is driven by community discussion, ideas, and code. Kohana developers are from all around the world, each with their own talents. This allows a rapid and flexible development cycle that can respond to bugs and requests within hours, instead of days or months.
5. GET, POST, COOKIE, and SESSION arrays all work as expected. Kohana does not limit your access to global data, but offers the same filtering and XSS protection that CodeIgniter does.
6. Cascading resources, modules, and inheritance. Controllers, models, libraries, helpers, and views can be loaded from any location within your system, application, or module paths. Configuration options are inherited and can by dynamically overwritten by each application.
7. No namespace conflicts. Class suffixes, like _Controller, are used to prevent namespace conflicts. This allows a User’s controller and Users model to both be loaded at the same time.
8. True auto-loading of classes. This includes libraries, controllers, models, and helpers. This is not pre-loading, but true dynamic loading of classes, as they are requested.
9. Helpers are static classes, not functions. For example, instead of using form_open(), you would use form::open().
10. Library drivers and API consistency. Libraries can use different “drivers” to handle different external APIs transparently. For example, multiple session storage options are available (database, cookie, and native), but the same interface is used for all of them. This allows new drivers to be developed for existing libraries, which keeps the API consistent and transparent.
11. Powerful event handler. Kohana events can by dynamically added to, replaced, or even removed completely. This allows many changes to Kohana execution process, without modification to existing system code.

As you can see, whilst maintaining a certain level of similarity to CodeIgniter, Kohana does offer some advantages (at the same time, some disadvantages). Let’s take a look at a few quick comparisons. Grading scale: Limited < Fair < Good < Excellent. Please note: if a feature is not available in the distributed package, but is available via 3rd party libraries, I will state that in the comparison. If a feature is available both in the distributed package and via 3rd party libraries, only the official one will get assessed.
Feature Comparison of CodeIgniter and Kohana Feature CodeIgniter 1.6.1 Kohana 2.1.1 Notes
License Apache/BSD-style new BSD Licenses are similar, although Kohana uses the new BSD license which is slightly more flexible than CI’s modified BSD license.
PHP compatibility 4.3.2+ and 5 5.1.3+ CodeIgniter supports PHP4 whilst Kohana is a stict PHP5 framework. If you are using PHP5 then Kohana offers more OOP and performance advantages. Start from version 2.2 (yet to be released), Kohana will only support PHP 5.2+.
Supported Databases MySQL (4.1+)
MySQLi
MS SQL
PostgreSQL
SQLite
Oracle
ODBC MySQL
PostgreSQL
SQLite CodeIgniter’s longer history ensures us a more widely available database support options than Kohana, although in the future Kohana is likely to support more databases too.
Community Forum
Wiki
Bug Tracker Forum
Trac
IRC CodeIgniter obviously has a much larger community and offers a wiki for community members to share tutorials and code snippets. Kohana on the other hand, has a smaller community, however the developers are actively online on the forum and IRC.
Documentation / User Guide Excellent Limited CodeIgniter is known for its excellent user guide. Kohana is in the process of improving its documentation.
Tutorial / Sample Availability Good Fair Tutorials are available on both of their forums. CodeIgniter has the advantage of having a wiki for easier navigation. Kohana on the other hand, has a dedicated tutorial page for some of the tutorials.
MVC Strict Strict Both frameworks use the same MVC approach.
Modular / HMVC Via 3rd party libraries Built in Kohana is built with HMVC in mind whilst CodeIgniter has some 3rd party libraries such as Matchbox and Modular HMVC to accomplish the same effect.
Conventions Flexible Flexible Unlike CakePHP, both of the frameworks offer flexible convensions. There are some defaults but most of them can be overwritten.
Configuration PHP files PHP files In my opinion Kohana is more configurable than CodeIgniter yet it is simpler (less clustered) to do so! Most of the Kohana configuration files are stored in the system folder, you only copy and paste the ones you actually need to modify, and modify them accordingly. CodeIgniter’s config files are all stored in the application folder.
Database Abstraction Modified ActiveRecord Modified ActiveRecord
ORM (optional) Both frameworks use the modified ActiveRecord pattern. Kohana has an optional ORM module. CodeIgniter has some ORM and Rails-style ActiveRecord implementation avaliable via 3rd party libraries.
ACL Via 3rd party libraries Auth library (optional) Neither of the frameworks forces you to use a specific ACL mechanism. CodeIgniter does not have one built in, and Kohana has one available as an optional module.
Validation Good Good Both frameworks offer a good built in validtion layer. Kohana 2.2 is planned to have some significant improvements for the validation library.
Caching Limited Fair In my opinion both of the caching features are limited. Kohana offers a slightly more useful cache library that supports file, SQLite, APC, eAccelerator, memcache, and Xcache based caching, with tag support.
Session Good Excellent CodeIgniter 1.6 has improved its session library, but it’s still inferior to Kohana’s implementation. Kohana’s session library supports both encryption and storing session data in database.
Logging / Debugging Good Excellent Both frameworks offer very good logging and debugging mechanisms. Kohana is a little bit ahead thanks to PHP5’s native Exception class and its powerful event handlers.
Templating Native PHP Native PHP Templating is *very* easy for both frameworks. If you can skin Wordpress, then you’d have no problems at all skinning CI or Kohana. If you want though, you can still incorporate one of the 3rd party templating solutions such as Smarty.
Helpers Good Good Helpers are usually libraries that used for simple, repetitive tasks. Both frameworks offer a wide range of helpers for handling forms, URLs and dates, etc.
JavaScript / AJAX N/A N/A Both frameworks respect your choice of JavaScript / AJAX frameworks. Unlike CakePHP and Ruby on Rails, they don’t have built-in helpers for any of the JavaScript libraries. This offers more flexibility as well as the use of unobtrusive JavaScript.
Web Services Fair Fair I could be wrong but I don’t think either framework supports (or at least encourages) RESTful design…
Localization Limited Good CodeIgniter has limited i18n support whilst Kohana offers a bit more (timezone / full UTF8 layer, etc).
Unit Testing Limited None * CodeIgniter’s built in unit testing class is very limited. * Kohana as of version 2.1.1 does not have a unit testing class, however it is planned for version 2.2.
The Verdict