Installation & Setup

Before you can build anything with CodeIgniter 4, you need a working local environment: the right PHP version, a handful of PHP extensions, and a copy of the framework itself. The officially supported (and by far the easiest) way to get a new project running is through Composer. This page walks through every step, from checking your server requirements to seeing the CodeIgniter welcome page in your browser.

1. Server Requirements

2. Installing via Composer

Composer is the standard PHP dependency manager, and it is the recommended way to install CodeIgniter 4. If you're new to Composer, the Composer track on this site covers it from scratch — the short version is that Composer downloads the framework and its dependencies into a vendor/ folder and wires up autoloading for you automatically.

Run the following command from the folder where you want your new project to live:

composer create-project codeigniter4/appstarter my_project

This downloads the appstarter skeleton — a ready-to-run CodeIgniter 4 application with sensible default configuration — into a new my_project folder. Once it finishes, move into that folder for all further commands:

cd my_project

3. Starting the Built-in Development Server

CodeIgniter ships with its own command-line utility called spark, sitting right at the root of every project. One of its most immediately useful commands starts a lightweight development server without needing Apache or Nginx configured at all:

php spark serve

By default this starts serving your application at http://localhost:8080. Open that address in a browser and, on a fresh install, you should see the CodeIgniter welcome page confirming everything is wired up correctly. If port 8080 is already in use, you can specify a different one:

php spark serve --port 8081

4. The spark CLI Tool

spark is CodeIgniter's built-in command-line tool, and serve is just one of the commands it offers. You will meet spark repeatedly throughout this track — it can generate boilerplate files (controllers, models, migrations), run database migrations, and list every registered route in your application, among many other things. For now, it's enough to know it exists and lives at the project root as the spark file, invoked with php spark <command>.

To see every command spark supports, run:

php spark list

5. Setting the Base URL and Environment

Two places control how your application identifies its own environment and base URL: the .env file at your project root, and app/Config/App.php. CodeIgniter ships with an env file (no leading dot) as a template — copy it to .env to activate it:

cp env .env

Inside .env, two settings matter most when you're just getting started: the environment name, and the base URL used to generate absolute links throughout your app.

# Switches error reporting, caching behaviour, and more
CI_ENVIRONMENT = development

# Used by base_url() and site_url() to build absolute links
app.baseURL = 'http://localhost:8080/'

Settings placed in .env override the matching properties in app/Config/App.php, which is the underlying configuration class. You can also set the base URL directly in that file if you prefer not to use .env:

<?php

namespace Config;

class App extends BaseConfig
{
    public $baseURL = 'http://localhost:8080/';
}

6. Verifying Your Install

With the dev server running (or your virtual host pointed at the right folder), load the base URL in a browser. A correct install shows CodeIgniter's default welcome page, which includes the framework version number and confirms PHP, the environment, and routing are all functioning together. If you see a blank page or an error instead, double-check the PHP version and extensions from step 1 first — most fresh-install problems trace back to a missing extension or an incompatible PHP version.

7. Top-Level Project Folders