Introduction to CodeIgniter in PHP

11/22/2025
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learn codeigniter for beginners

Introduction to CodeIgniter in PHP

Introduction to CodeIgniter in PHP: Beginner-Friendly Tutorial

CodeIgniter is a lightweight, high-performance PHP framework designed to help developers build dynamic web applications quickly and efficiently. Known for its small footprint, simple architecture, and excellent speed, CodeIgniter remains a popular choice for both beginners and intermediate developers.

This tutorial introduces CodeIgniter, its features, installation steps, and how to build your first application using this powerful PHP framework.

What is CodeIgniter?

CodeIgniter is an open-source PHP framework that uses the MVC (Model-View-Controller) architecture to separate the application logic from the user interface. It is ideal for developers who want a simple and efficient framework without unnecessary overhead.

Key Benefits of CodeIgniter

  • Extremely fast and lightweight

  • Easy to learn and use

  • Minimal configuration

  • Excellent documentation

  • Built-in security features

  • Great for small-to-medium web applications

Core Features of CodeIgniter

1. MVC Architecture

CodeIgniter follows the MVC pattern for structured and scalable development.

2. Lightweight Framework

The full installation is less than 5 MB, making it one of the smallest PHP frameworks.

3. Built-in Security Tools

Includes protections against:

  • XSS

  • CSRF

  • SQL Injection

  • Input filtering

4. Form and URL Helpers

CodeIgniter provides helper functions for forms, URLs, strings, cookies, and more.

5. Database Abstraction Layer

Supports multiple databases with Query Builder for simpler and safer queries.

Example:

$query = $this->db->get('users');

6. Error Handling & Debugging

Provides detailed error reporting for faster development.

7. Session Management

Simple and secure session control.

Installing CodeIgniter

Follow these steps to get started.

Step 1: Download CodeIgniter

Download from the official site:

https://codeigniter.com

Extract it into your web server directory (htdocs for XAMPP, www for WAMP).

Step 2: Configure Base URL

Edit application/config/config.php:

$config['base_url'] = 'http://localhost/codeigniter/';

Step 3: Test Installation

Open in browser:

http://localhost/codeigniter/

You should see the CodeIgniter welcome page.

Understanding CodeIgniter Directory Structure

application/     # Main application logic
system/          # Core CodeIgniter files
public/          # Public resources

Key Folders

  • controllers/ – Handles requests

  • models/ – Interacts with database

  • views/ – Displays data to users

Creating Your First Controller

Create file: application/controllers/Welcome.php

<?php
class Welcome extends CI_Controller {
    public function index() {
        echo "Welcome to CodeIgniter!";
    }
}

Visit:

http://localhost/codeigniter/welcome

Creating Your First View

Create file: application/views/home.php

<h1>Hello from CodeIgniter!</h1>

Update controller:

public function home() {
    $this->load->view('home');
}

Access:

http://localhost/codeigniter/welcome/home

Connecting CodeIgniter to a Database

Edit application/config/database.php:

'hostname' => 'localhost',
'username' => 'root',
'password' => '',
'database' => 'mydb',

Simple Database Query Example

Controller:

public function users() {
    $query = $this->db->get('users');
    print_r($query->result());
}

Why Choose CodeIgniter?

  • Super-fast performance

  • Ideal for shared hosting

  • Small learning curve

  • Simple configuration and folder structure

  • Easy for beginners transitioning from core PHP

Conclusion

CodeIgniter remains a powerful PHP framework for developers who want simplicity, speed, and control. With its lightweight design, MVC architecture, built-in security features, and excellent documentation, it is an excellent choice for building small-to-medium web applications.

This introduction provides all the basics you need to begin your CodeIgniter journey—install it, configure it, and start building your first app today.

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