Installing CodeIgniter: A Beginner's Guide to PHP Framework Setup

CodeIgniter is a lightweight, powerful PHP framework that helps you build web applications quickly using the Model-View-Controller (MVC) pattern. It is known for its simplicity, speed, and excellent documentation.

Installation

# Recommended: via Composer
composer create-project codeigniter4/appstarter my-project

# Set directory permissions (Linux / macOS)
chmod -R 755 my-project
chmod -R 777 my-project/writable

# Configure base URL — edit app/Config/App.php
public $baseURL = 'http://localhost/my-project/';

# Set environment — edit .env
CI_ENVIRONMENT = development

Directory Structure

Directory	Purpose
`app/`	Your application — Controllers, Models, Views
`public/`	Public entry point (`index.php`) and static assets
`writable/`	Logs, cache, and session files
`tests/`	Unit and feature tests
`vendor/`	Composer dependencies

Your First Controller

<?php
// app/Controllers/Home.php
namespace App\Controllers;

class Home extends BaseController
{
    public function index()
    {
        return view('welcome_message');
    }

    public function about()
    {
        $data = [
            'title'   => 'About Us',
            'message' => 'Welcome to our website!',
        ];
        return view('about', $data);
    }
}

Your First View

<!-- app/Views/about.php -->
<!DOCTYPE html>
<html>
<head><title><?= esc($title) ?></title></head>
<body>
  <h1><?= esc($title) ?></h1>
  <p><?= esc($message) ?></p>
</body>
</html>

Routing

// app/Config/Routes.php
$routes->get('/',       'Home::index');
$routes->get('/about',  'Home::about');
$routes->get('/user/(:num)', 'User::profile/$1');

Database Configuration

# .env
database.default.hostname = localhost
database.default.database = my_database
database.default.username = root
database.default.password =
database.default.DBDriver = MySQLi
database.default.port     = 3306

// Using the database in a controller
$db      = \Config\Database::connect();
$query   = $db->query("SELECT * FROM users");
$results = $query->getResultArray();

Why CodeIgniter for Beginners

Simple MVC — easy to understand and reason about
Excellent docs — comprehensive user guide with real examples
Lightweight — small footprint, fast responses even on shared hosting
Built-in libraries — email, sessions, form validation, file upload out of the box
Active community — answers to most problems are one search away