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.

What are Configuration Classes?

Configuration classes are utilized to define system default configuration values. System configuration values are typically static. Configuration classes are intended to retain the settings that configure how the application operates, rather than responding to each user’s individual settings.

It is not recommended to alter values set during the instantiation of a configuration class later during execution. In other words, it is recommended to treat configuration classes as immutable or readonly classes. This is especially important if you utilize Config Caching.

Configuration values can be hard-coded in the class files or obtained from environment variables at instantiation.

Working with Configuration Files

Getting a Config Object

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

new keyword

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');
$config = config(\Config\Pager::class);

// Creating a new object with config function
$config = config('Pager', false);

If no namespace is provided, it will look for the file in the app/Config folder first, and if not found, look for in the Config folder in all defined namespaces.

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.


Prior to v4.4.0, config() finds the file in app/Config/ when there is a class with the same shortname, even if you specify a fully qualified class name like config(\Acme\Blog\Config\Blog::class). This behavior has been fixed in v4.4.0, and returns the specified instance.

Getting a Config Property

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;

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.

You can put configuration files in any Config folder by using a different namespace.

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:


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.

Dotenv File

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”.

Creating Dotenv File

CodeIgniter expects the .env file to be at the root of your project alongside the 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.

Setting Variables

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.

Getting Variables

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'];


Note that your settings from the .env file are added to $_SERVER and $_ENV. As a side effect, this means that if your CodeIgniter application is (for example) generating a var_dump($_ENV) or phpinfo() (for debugging or other valid reasons), or a detailed error report in the development environment is shown, your secure credentials are publicly exposed.

Nesting Variables

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

BASE_DIR = "/var/webroot/project-root"
CACHE_DIR = "${BASE_DIR}/cache"
TMP_DIR = "${BASE_DIR}/tmp"

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"
db = my_db

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

Namespace Separator

Some environments, e.g., Docker, CloudFormation, do not permit variable name with dots (.). In such case, since v4.1.5, you could also use underscores (_) as a separator.

// namespaced variables with underscore
app_forceGlobalSecureRequests = true
app_CSPEnabled = true

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.


You cannot add a new property by setting environment variables, nor change a scalar value to an array. See Environment Variables as Replacements for Data.


This feature is implemented in the CodeIgniter\Config\BaseConfig class. So it will not work with a few files in the app/Config folder that do not extends the class.

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.forceGlobalSecureRequests = true
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.forceGlobalSecureRequests = true
app.CSPEnabled = true

Since v4.1.5, you can also write with underscores:

app_forceGlobalSecureRequests = true
app_CSPEnabled = true


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

Environment Variables as Replacements for Data

It is very important to always remember that environment variables contained in your .env are only replacements for existing scalar values.

Simply put, you can change only the property’s scalar value that exists in the Config class by setting it in your .env.

  1. You cannot add a property that is not defined in the Config class.

  2. You cannot change a scalar value in a property to an array.

  3. You cannot add an element to an existing array.

For example, you cannot just put app.myNewConfig = foo in your .env and expect your Config\App to magically have that property and value at run time.

When you have the property $default = ['encrypt' => false] in your Config\Database, you cannot change the encrypt value to an array even if you put database.default.encrypt.ssl_verify = true in your .env. If you want to do like that, see Database Configuration.

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\ = George

// array namespaced variables
Config\ = "Berlin"
Config\ = "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\ = "Berlin" = "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 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.


“Registrars” are any other classes which might provide additional configuration properties. Registrars provide a means of altering a configuration at runtime across namespaces and files.

Registrars work if Auto-Discovery is enabled in Modules. It alters configuration properties when the Config object is instantiated.

There are two ways to implement a Registrar: implicit and explicit.


Values from .env always take priority over Registrars.

Implicit Registrars

Implicit Registrars can change any Config class properties.

Any namespace may define implicit registrars by using the Config/Registrar.php file. These files are classes whose methods are named for each configuration class you wish to extend.

For example, a third-party module or Composer package might wish to supply an additional template to Config\Pager without overwriting whatever a developer has already configured. In src/Config/Registrar.php there would be a Registrar class with the single Pager() method (note the case-sensitivity):


namespace CodeIgniter\Shield\Config;

class Registrar
    public static function Pager(): array
        return [
            'templates' => [
                'module_pager' => 'MyModule\Views\Pager',

Registrar methods must always return an array, with keys corresponding to the properties of the target config file. Existing values are merged, and Registrar properties have overwrite priority.

Explicit Registrars

Explicit Registrars can only change the Config class properties in which they are registered.

A configuration file can also specify any number of registrars explicitly. This is done by adding a $registrars property to your configuration file, holding an array of the names of candidate registrars:


namespace Config;

// ...

class MyConfig extends BaseConfig
    public static $registrars = [

    // ...

In order to act as a “registrar” the classes so identified must have a static function with the same name 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 it will invoke the method named for the configuration class and incorporate any returned properties.

A sample configuration class setup for this:


namespace Config;

use CodeIgniter\Config\BaseConfig;

class MySalesConfig extends BaseConfig
    public int $target        = 100;
    public string $campaign   = 'Winter Wonderland';
    public static $registrars = [

… and the associated regional sales model might look like:


namespace App\Models;

class RegionalSales
    public static function MySalesConfig(): array
        return [
            'target' => 45,

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


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

Confirming Config Values

The actual Config object property values are changed at runtime by the Registrars and Environment Variables, and Config Caching.

CodeIgniter has the following command to check the actual Config values.


Added in version 4.5.0.

For example, if you want to check the Config\App instance:

php spark config:check App

The output is like the following:

Config\App#6 (12) (
    public 'baseURL' -> string (22) "http://localhost:8080/"
    public 'allowedHostnames' -> array (0) []
    public 'indexPage' -> string (9) "index.php"
    public 'uriProtocol' -> string (11) "REQUEST_URI"
    public 'defaultLocale' -> string (2) "en"
    public 'negotiateLocale' -> boolean false
    public 'supportedLocales' -> array (1) [
        0 => string (2) "en"
    public 'appTimezone' -> string (3) "UTC"
    public 'charset' -> string (5) "UTF-8"
    public 'forceGlobalSecureRequests' -> boolean false
    public 'proxyIPs' -> array (0) []
    public 'CSPEnabled' -> boolean false

Config Caching: Disabled

You can see if Config Caching is eabled or not.


If Config Caching is enabled, the cached values are used permanently. See Config Caching for details.