/CodeIgniter 4


Every framework uses configuration files to define numerous parameters and initial settings. CodeIgniter configuration files define simple classes where the required settings are public properties.

Unlike many other frameworks, CodeIgniter configurable items aren’t contained in a single file. Instead, each class that needs configurable items will have a configuration file with the same name as the class that uses it. You will find the application configuration files in the /app/Config folder.

Working With Configuration Files

You can access configuration files for your classes in several different ways.

  • By using the new keyword to create an instance:

    // Creating new configuration object by hand
    $config = new \Config\Pager();
  • By using the config() function:

    // Get shared instance with config function
    $config = config('Pager');
    // Access config class with namespace
    $config = config( 'Config\\Pager' );
    // Creating a new object with config function
    $config = config('Pager', false);

All configuration object properties are public, so you access the settings like any other property:

$config = config('Pager');
// Access settings as object properties
$pageSize = $config->perPage;

If no namespace is provided, it will look for the file in all defined namespaces as well as /app/Config/.

All of the configuration files that ship with CodeIgniter are namespaced with Config. Using this namespace in your application will provide the best performance since it knows exactly where to find the files.

You can put configuration files in any folder you want by using a different namespace. This allows you to put configuration files on the production server in a folder that is not web-accessible while keeping it under /app for easy access during development.

Creating Configuration Files

When you need a new configuration, first you create a new file at your desired location. The default file location (recommended for most cases) is /app/Config. The class should use the appropriate namespace, and it should extend CodeIgniter\Config\BaseConfig to ensure that it can receive environment-specific settings.

Define the class and fill it with public properties that represent your settings.:

<?php namespace Config;

use CodeIgniter\Config\BaseConfig;

class CustomClass extends BaseConfig
    public $siteName  = 'My Great Site';
    public $siteEmail = '[email protected]';


Environment Variables

One of today’s best practices for application setup is to use Environment Variables. One reason for this is that Environment Variables are easy to change between deploys without changing any code. Configuration can change a lot across deploys, but code does not. For instance, multiple environments, such as the developer’s local machine and the production server, usually need different configuration values for each particular setup.

Environment Variables should also be used for anything private such as passwords, API keys, or other sensitive data.

Environment Variables and CodeIgniter

CodeIgniter makes it simple and painless to set Environment Variables by using a “dotenv” file. The term comes from the file name, which starts with a dot before the text “env”.

CodeIgniter expects .env to be at the root of your project alongside the system and app directories. There is a template file distributed with CodeIgniter that’s located at the project root named env (Notice there’s no dot (.) at the start?). It has a large collection of variables your project might use that have been assigned empty, dummy, or default values. You can use this file as a starting place for your application by either renaming the template to .env, or by making a copy of it named .env.


Make sure the .env file is NOT tracked by your version control system. For git that means adding it to .gitignore. Failure to do so could result in sensitive credentials being exposed to the public.

Settings are stored in .env files as a simple a collection of name/value pairs separated by an equal sign.

S3_BUCKET = dotenv
SECRET_KEY = super_secret_key
CI_ENVIRONMENT = development

When your application runs, .env will be loaded automatically, and the variables put into the environment. If a variable already exists in the environment, it will NOT be overwritten. The loaded Environment variables are accessed using any of the following: getenv(), $_SERVER, or $_ENV.

$s3_bucket = getenv('S3_BUCKET');
$s3_bucket = $_ENV['S3_BUCKET'];
$s3_bucket = $_SERVER['S3_BUCKET'];

Nesting Variables

To save on typing, you can reuse variables that you’ve already specified in the file by wrapping the variable name within ${...}


Namespaced Variables

There will be times when you will have several variables with the same name. The system needs a way of knowing what the correct setting should be. This problem is solved by “namespacing” the variables.

Namespaced variables use a dot notation to qualify variable names so they will be unique when incorporated into the environment. This is done by including a distinguishing prefix followed by a dot (.), and then the variable name itself.

// not namespaced variables
name = "George"

// namespaced variables
address.city = "Berlin"
address.country = "Germany"
frontend.db = sales
backend.db = admin
BackEnd.db = admin

Configuration Classes and Environment Variables

When you instantiate a configuration class, any namespaced environment variables are considered for merging into the configuration object’s properties.

If the prefix of a namespaced variable exactly matches the namespace of the configuration class, then the trailing part of the setting (after the dot) is treated as a configuration property. If it matches an existing configuration property, the environment variable’s value will replace the corresponding value from the configuration file. If there is no match, the configuration class properties are left unchanged. In this usage, the prefix must be the full (case-sensitive) namespace of the class.

Config\App.CSRFProtection  = true
Config\App.CSRFCookieName = csrf_cookie
Config\App.CSPEnabled = true


Both the namespace prefix and the property name are case-sensitive. They must exactly match the full namespace and property names as defined in the configuration class file.

The same holds for a short prefix, which is a namespace using only the lowercase version of the configuration class name. If the short prefix matches the class name, the value from .env replaces the configuration file value.

app.CSRFProtection  = true
app.CSRFCookieName = csrf_cookie
app.CSPEnabled = true


When using the short prefix the property names must still exactly match the class defined name.

Treating Environment Variables as Arrays

A namespaced environment variable can be further treated as an array. If the prefix matches the configuration class, then the remainder of the environment variable name is treated as an array reference if it also contains a dot.

// regular namespaced variable
Config\SimpleConfig.name = George

// array namespaced variables
Config\SimpleConfig.address.city = "Berlin"
Config\SimpleConfig.address.country = "Germany"

If this was referring to a SimpleConfig configuration object, the above example would be treated as:

$address['city']    = "Berlin";
$address['country'] = "Germany";

Any other elements of the $address property would be unchanged.

You can also use the array property name as a prefix. If the environment file held the following then the result would be the same as above.

// array namespaced variables
Config\SimpleConfig.address.city = "Berlin"
address.country = "Germany"

Handling Different Environments

Configuring multiple environments is easily accomplished by using a separate .env file with values modified to meet that environment’s needs.

The file should not contain every possible setting for every configuration class used by the application. In truth, it should include only those items that are specific to the environment or are sensitive details like passwords and API keys and other information that should not be exposed. But anything that changes between deployments is fair-game.

In each environment, place the .env file in the project’s root folder. For most setups, this will be the same level as the system and app directories.

Do not track .env files with your version control system. If you do, and the repository is made public, you will have put sensitive information where everybody can find it.


A configuration file can also specify any number of “registrars”, which are any other classes which might provide additional configuration properties. This is done by adding a registrars property to your configuration file, holding an array of the names of candidate registrars.:

protected $registrars = [

In order to act as a “registrar” the classes so identified must have a static function named the same as the configuration class, and it should return an associative array of property settings.

When your configuration object is instantiated, it will loop over the designated classes in $registrars. For each of these classes, which contains a method name matching the configuration class, it will invoke that method, and incorporate any returned properties the same way as described for namespaced variables.

A sample configuration class setup for this:

<?php namespace App\Config;

use CodeIgniter\Config\BaseConfig;

class MySalesConfig extends BaseConfig
    public $target        = 100;
    public $campaign      = "Winter Wonderland";
    protected $registrars = [

… and the associated regional sales model might look like:

<?php namespace App\Models;

class RegionalSales
    public static function MySalesConfig()
        return ['target' => 45, 'actual' => 72];

With the above example, when MySalesConfig is instantiated, it will end up with the two properties declared, but the value of the $target property will be over-ridden by treating RegionalSalesModel as a “registrar”. The resulting configuration properties:

$target   = 45;
$campaign = "Winter Wonderland";

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