CodeIgniter 4 is a rewrite of the framework. On February 24, 2020, which would be Jim Perry’s birthday, CodeIgniter 4 was launched. Between the launch of the first stable version of CodeIgniter 3 and CodeIgniter 4, it took almost 5 years.

The “lean, mean, and simple” philosophy has been retained, but the implementation has a lot of differences, compared to CodeIgniter 3.

CodeIgniter 4 is very different from 3 and below you will see the main differences between them.

1. PHP versions

  • CodeIgniter 4 required minimum PHP version 7.2
  • CodeIgniter 3 it is possible to use PHP version 5.6 (The developers of PHP are no longer supporting PHP 5.6)

2. Composer

  • CodeIgniter 4 can be download in two ways
    #1 Available as a ready-to-run zip or tarball.
    #2 It can also be installed using Composer
  • CodeIgniter 3 can not be installed using composer

3. Directory Structure

  • CodeIgniter 4 devided into 5 directory /app,/system,/public,/writable,/tests
  • CodeIgniter 3 has 2 directories:/application and /system`

4. Namespaces

  • CodeIgniter 4 is built for PHP7.2+, and everything in the framework is namespaced, except for the helpers.
  • CodeIgniter 3 does not use namespaces.

5. Autoloading

  • CodeIgniter 4 has a autoload process of class, by use of namespaces
  • CodeIgniter 3 has a manual process to configure most of the files to be loaded.

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