The CodeIgniter Framework defines a constant value, CI_VERSION, which is set to the current version of CodeIgniter. The value is defined in the framework’s core libraries and can most usually be found in your project’s system directory in the file /system/core/CodeIgniter.php. Here’s an example of what that looks like in the file:
If you’re inside of a console, terminal, or command line interface, you can use the handy command grep to search for the version number. Follow the instructions below as an example:
# navigate to the webroot path of your project
cd /path/to/www.yoursite.com/
# recursively search for any mentions of CI_VERSION in the /system directory
grep -r CI_VERSION system/
# the system output should show something similar to the following:
# system/=/core/CodeIgniter.php: define('CI_VERSION', '3.0.4');
As you can see from the above search, the example application is running on version 3.0.4.