# CodeIgniter User Guide Version 2.2.0

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# Config Class

The Config class provides a means to retrieve configuration preferences. These preferences can come from the default config file (`application/config/config.php`) or from your own custom config files.

Note: This class is initialized automatically by the system so there is no need to do it manually.

## Anatomy of a Config File

By default, CodeIgniter has one primary config file, located at `application/config/config.php`. If you open the file using your text editor you'll see that config items are stored in an array called $config.

You can add your own config items to this file, or if you prefer to keep your configuration items separate (assuming you even need config items), simply create your own file and save it in config folder.

Note: If you do create your own config files use the same format as the primary one, storing your items in an array called $config. CodeIgniter will intelligently manage these files so there will be no conflict even though the array has the same name (assuming an array index is not named the same as another).

## Loading a Config File

Note: CodeIgniter automatically loads the primary config file (`application/config/config.php`), so you will only need to load a config file if you have created your own.

There are two ways to load a config file:

1. Manual Loading

   To load one of your custom config files you will use the following function within the controller that needs it:

   `$this->config->load('filename');`

   Where filename is the name of your config file, without the .php file extension.

   If you need to load multiple config files normally they will be merged into one master config array. Name collisions can occur, however, if you have identically named array indexes in different config files. To avoid collisions you can set the second parameter to `TRUE` and each config file will be stored in an array index corresponding to the name of the config file. Example:

   `// Stored in an array with this prototype: $this->config['blog_settings'] = $config
   $this->config->load('blog_settings', `TRUE`);`

   Please see the section entitled Fetching Config Items below to learn how to retrieve config items set this way.

   The third parameter allows you to suppress errors in the event that a config file does not exist:

   `$this->config->load('blog_settings', FALSE, `TRUE`);`
2. Auto-loading

   If you find that you need a particular config file globally, you can have it loaded automatically by the system. To do this, open the autoload.php file, located at `application/config/autoload.php`, and add your config file as indicated in the file.

## Fetching Config Items

To retrieve an item from your config file, use the following function:

`$this->config->item('item name');`

Where item name is the $config array index you want to retrieve. For example, to fetch your language choice you'll do this:

`$lang = $this->config->item('language');`

The function returns FALSE (boolean) if the item you are trying to fetch does not exist.

If you are using the second parameter of the `$this->config->load` function in order to assign your config items to a specific index you can retrieve it by specifying the index name in the second parameter of the `$this->config->item()` function. Example:

`// Loads a config file named blog_settings.php and assigns it to an index named "blog_settings"
$this->config->load('blog_settings', `TRUE`);
// Retrieve a config item named site_name contained within the blog_settings array
$site_name = $this->config->item('site_name', 'blog_settings');
// An alternate way to specify the same item:
$blog_config = $this->config->item('blog_settings');
$site_name = $blog_config['site_name'];`

## Setting a Config Item

If you would like to dynamically set a config item or change an existing one, you can do so using:

`$this->config->set_item('item_name', 'item_value');`

Where item_name is the $config array index you want to change, and item_value is its value.

## Environments

You may load different configuration files depending on the current environment. The `ENVIRONMENT` constant is defined in index.php, and is described in detail in the Handling Environments section.

To create an environment-specific configuration file, create or copy a configuration file in application/config/{ENVIRONMENT}/{FILENAME}.php

For example, to create a production-only config.php, you would:

1. Create the directory application/config/production/
2. Copy your existing config.php into the above directory
3. Edit application/config/production/config.php so it contains your production settings

When you set the `ENVIRONMENT` constant to 'production', the settings for your new production-only config.php will be loaded.

You can place the following configuration files in environment-specific folders:

- Default CodeIgniter configuration files
- Your own custom configuration files

Note: CodeIgniter always tries to load the configuration files for the current environment first. If the file does not exist, the global config file (i.e., the one in `application/config/`) is loaded. This means you are not obligated to place all of your configuration files in an environment folder − only the files that change per environment.

## Helper Functions

The config class has the following helper functions:

## $this->config->site_url();

This function retrieves the URL to your site, along with the "index" value you've specified in the config file.

## $this->config->base_url();

This function retrieves the URL to your site, plus an optional path such as to a stylesheet or image.

The two functions above are normally accessed via the corresponding functions in the URL Helper.

## $this->config->system_url();

This function retrieves the URL to your system folder.