The CodeIgniter framework allows you to set an ENVIRONMENT constant in your bootstrap index.php file. This constant can be used to pull in different configuration information. However, it can become a hassle to remember to change that value when you switch environments. FUEL has added the ability to set up an array of server host values that correspond to different environments and will automatically set the ENVIRONMENT constant value. To set your environments, edit the /fuel/application/config/environments.php file. If there is no matching environment it is setup to default to the development environment. The default can be changed in the index.php bootstrap file.
The /fuel/application/config/environments.php file by default includes the following development environments:
$environments = array( 'development' => array('localhost*', '192.*', '*.dev'), );
You can use regular expression or asterisks as a wildcards.