CodeIgniter 3 Download: How to Install and Use the PHP Framework
CodeIgniter is one of the most popular and powerful PHP frameworks that is used for developing dynamic web applications. It is known for its simplicity, performance, and security. CodeIgniter 3 is the legacy version of the framework that supports PHP 5.6 and above. In this article, we will show you how to download, install, and use CodeIgniter 3 to create your own web projects.
What is CodeIgniter 3?
CodeIgniter 3 is an open-source PHP framework that follows the model-view-controller (MVC) design pattern. It provides a set of libraries and helpers that enable common web development tasks, such as database access, form validation, email sending, session management, image manipulation, and more. CodeIgniter 3 also has a lightweight core that allows for fast loading and execution of the code.
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Features of CodeIgniter 3
Some of the main features of CodeIgniter 3 are:
Model-View-Controller Based System: CodeIgniter 3 separates the logic, presentation, and data layers of the application, making it easier to maintain and extend.
Extremely Light Weight: CodeIgniter 3 has a small footprint of about 2 MB, which makes it fast and efficient.
Full Featured Database Classes: CodeIgniter 3 supports several database platforms, such as MySQL, PostgreSQL, SQLite, Oracle, MS SQL, and more. It also provides a query builder class that simplifies the creation and execution of SQL queries.
Form and Data Validation: CodeIgniter 3 has a built-in form validation library that allows you to validate user input data using various rules and filters.
Security and XSS Filtering: CodeIgniter 3 has several security features, such as CSRF protection, input sanitization, output escaping, encryption, and more.
Session Management: CodeIgniter 3 has a session library that handles the creation, retrieval, and destruction of session data using various storage options, such as files, cookies, or database.
Email Sending Class: CodeIgniter 3 has an email library that enables you to send emails using various protocols, such as mail, sendmail, or SMTP. It also supports attachments, HTML or text emails, multiple recipients, and more.
Image Manipulation Library: CodeIgniter 3 has an image library that allows you to perform various operations on images, such as cropping, resizing, rotating, watermarking, and more. It supports GD, ImageMagick, and NetPBM libraries.
File Uploading Class: CodeIgniter 3 has a file uploading library that facilitates the uploading of files from the user's browser to the server. It also provides options to set file size limits, file type restrictions, file name preferences, and more.
FTP Class: CodeIgniter 3 has an FTP library that enables you to connect to an FTP server and perform various file operations, such as uploading, downloading, renaming, deleting, and more.
Pagination Class: CodeIgniter 3 has a pagination library that helps you create links for paginated data sets.
Template Parser Class: CodeIgniter 3 has a template parser class that allows you to use simple pseudo-variables in your views and replace them with actual data at runtime.
Error Logging: CodeIgniter 3 has an error logging class that logs any errors or exceptions that occur in your application to a file or database.
Benchmarking: CodeIgniter 3 has a benchmarking class that measures the execution time and memory usage of your application.
Documentation: CodeIgniter 3 has a comprehensive and user-friendly documentation that covers all the aspects of the framework.
Requirements for CodeIgniter 3
To use CodeIgniter 3, you need to have the following requirements:
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A web server that supports PHP, such as Apache, Nginx, or IIS.
PHP version 5.6 or higher.
A database server, such as MySQL, PostgreSQL, SQLite, Oracle, MS SQL, or any other supported by CodeIgniter 3.
A web browser that supports HTML, CSS, and JavaScript.
A text editor or an IDE that supports PHP syntax highlighting and code completion.
How to Download and Install CodeIgniter 3
There are two ways to download and install CodeIgniter 3: manual download and installation, or composer installation.
Manual Download and Installation
To manually download and install CodeIgniter 3, follow these steps:
Go to the official website of CodeIgniter 3 at and download the latest version of the framework.
Extract the downloaded zip file to a folder on your local machine or your web server.
Rename the folder to whatever you want, such as "codeigniter" or "my_project".
Open the folder and locate the file named "index.php". This is the main entry point of your application.
Open the file with your text editor or IDE and change the value of the constant "$system_path" to point to the location of the "system" folder inside your CodeIgniter 3 folder. For example, if your CodeIgniter 3 folder is named "codeigniter" and is located in the root directory of your web server, then you can set the value as follows:
$system_path = 'codeigniter/system';
If you want to move the "system" folder outside your web root for security reasons, then you need to provide the full path to the folder. For example, if you move the "system" folder to "/var/www/system", then you can set the value as follows:
$system_path = '/var/www/system';
Similarly, you can change the value of the constant "$application_folder" to point to the location of the "application" folder inside your CodeIgniter 3 folder. This is where you will store all your custom code, such as controllers, models, views, libraries, helpers, and more. By default, it is set to "application", which means it is located inside your CodeIgniter 3 folder. You can change it to any other name or location as per your preference.
Save and close the file.
You have successfully installed CodeIgniter 3 on your machine or server. You can test it by opening your web browser and typing the URL of your CodeIgniter 3 folder. For example, if your CodeIgniter 3 folder is named "codeigniter" and is located in the root directory of your web server, then you can type . You should see a welcome page that says "Welcome to CodeIgniter!"
Composer Installation
If you are familiar with Composer, a dependency manager for PHP, then you can use it to download and install CodeIgniter 3. To do so, follow these steps:
Make sure you have Composer installed on your machine or server. If not, you can download it from and follow the installation instructions.
Create a new project folder on your local machine or your web server and navigate to it using your terminal or command prompt.
Type the following command to create a new CodeIgniter 3 project using Composer:
composer create-project codeigniter/framework codeigniter
This will create a new folder named "codeigniter" inside your project folder and download all the necessary files and dependencies for CodeIgniter 3.
You have successfully installed CodeIgniter 3 using Composer. You can test it by opening your web browser and typing the URL of your project folder. For example, if your project folder is named "my_project" and is located in the root directory of your web server, then you can type . You should see a welcome page that says "Welcome to CodeIgniter!"
How to Use CodeIgniter 3
Now that you have downloaded and installed CodeIgniter 3, you can start using it to create your own web applications. In this section, we will give you a brief overview of how to use CodeIgniter 3 and its main components.
Basic Structure of CodeIgniter 3
CodeIgniter 3 has a basic structure that consists of three main folders: system, application, and public.
The system folder contains the core files of the framework, such as libraries, helpers, drivers, and more. You should not modify or delete any files in this folder, as it may affect the functionality of the framework.
The application folder contains your custom code, such as controllers, models, views, libraries, helpers, and more. This is where you will write most of your code and store your application-specific configurations, such as database settings, routes, hooks, and more.
The public folder contains your public assets, such as images, CSS files, JavaScript files, and more. This is where you will store your static files that are accessible by the web browser.
The index.php file is the main entry point of your application. It loads the system and application files and processes the incoming requests. You can change some settings in this file, such as the environment mode (development or production), the error reporting level, and the base URL of your application.
Model-View-Controller Architecture
CodeIgniter 3 follows the model-view-controller (MVC) design pattern, which is a common way of organizing web applications. The MVC pattern separates the logic, presentation, and data layers of the application into three components: models, views, and controllers.
Models are classes that handle the data and business logic of the application. They interact with the database or other data sources and provide methods for retrieving, inserting, updating, and deleting data.
Views are files that contain the HTML output of the application. They display the data provided by the models or controllers in a user-friendly format.
Controllers are classes that handle the user requests and responses. They receive input from the user or the web server, load the appropriate models and views, and send output to the browser.
The MVC pattern allows for a clear separation of concerns and a modular structure of the application. It also makes it easier to reuse code and maintain and extend the application.
Routing and Controllers
Routing is the process of matching a URL to a controller and a method. CodeIgniter 3 uses a segment-based approach for routing, which means that each segment of the URL corresponds to a controller or a method. For example, if you have a URL like , then CodeIgniter 3 will try to load the Users controller and call its profile method with 123 as a parameter.
You can define your own custom routes in the file application/config/routes.php. This file contains an array named $route that maps URLs to controllers and methods. For example, if you want to route to Pages controller and about method, then you can add this line to the $route array:
$route['about'] = 'pages/about';
You can also use regular expressions or wildcards to create dynamic routes that match multiple URLs. For example, if you want to route any URL that starts with to Blog controller and index method with the rest of the URL as a parameter, then you can add this line to the $route array:
$route['blog/(.*)'] = 'blog/index/$1';
To create controllers in CodeIgniter 3, you need to create a class that extends CI_Controller in the file application/controllers/Controller_name.php. The class name and the file name should be capitalized and match each other. For example, if you want to create a Users controller, then you need to create a file named Users.php in application/controllers folder with this code:
<?php defined('BASEPATH') OR exit('No direct script access allowed'); class Users extends CI_Controller public function __construct() parent::__construct(); // Load any models or libraries here public function index() // This is the default method for the Users controller // You can load views or data here public function profile($id) // This is a custom method for the Users controller // It takes a parameter $id from the URL // You can load views or data here // You can add more methods here as per your requirement
To call a controller method, you need to use the syntax $this->method_name(). For example, if you want to call the profile method of the Users controller from the index method, then you can use this code:
$this->profile(123);
You can also pass data to the controller methods using an array or an object. For example, if you want to pass an array of user data to the profile method, then you can use this code:
$user_data = array( 'name' => 'John Doe', 'email' => 'johndoe@example.com', 'age' => 25 ); $this->profile($user_data);
Views and Templates
Views are files that contain the HTML output of the application. They are usually stored in the application/views folder and have a .php extension. To create a view in CodeIgniter 3, you need to create a file with the name of the view and write your HTML code inside it. For example, if you want to create a view named welcome.php, then you need to create a file named welcome.php in application/views folder with this code:
<html>
<head>
<title>Welcome to CodeIgniter!</title>
</head>
<body>
<h1>Welcome to CodeIgniter!</h1>
<p>This is a simple view file.</p>
</body>
</html>
To load a view from a controller, you need to use the syntax $this->load->view('view_name'). For example, if you want to load the welcome view from the index method of the Users controller, then you can use this code:
$this->load->view('welcome');
You can also pass data to the views using an array or an object. For example, if you want to pass an array of user data to the welcome view, then you can use this code:
$user_data = array( 'name' => 'John Doe', 'email' => 'johndoe@example.com', 'age' => 25 ); $this->load->view('welcome', $user_data);
To access the data in the view, you need to use the syntax $variable_name. For example, if you want to display the user name in the welcome view, then you can use this code:
<h1>Welcome to CodeIgniter, <?php echo $name; ?>!</h1>
CodeIgniter 3 also provides a template parser class that allows you to use simple pseudo-variables in your views and replace them with actual data at runtime. To use the template parser class, you need to load it using $this->load->library('parser') and then use the syntax $this->parser->parse('view_name', $data). For example, if you want to use the template parser class to load the welcome view with user data, then you can use this code:
$this->load->library('parser'); $user_data = array( 'name' => 'John Doe', 'email' => 'johndoe@example.com', 'age' => 25 ); $this->parser->parse('welcome', $user_data);
To use pseudo-variables in your views, you need to enclose them in curly braces. For example, if you want to display the user name in the welcome view using pseudo-variables, then you can use this code:
<h1>Welcome to CodeIgniter, name!</h1>
Models and Database Access
Models are classes that handle the data and business logic of the application. They interact with the database or other data sources and provide methods for retrieving, inserting, updating, and deleting data.
To create models in CodeIgniter 3, you need to create a class that extends CI_Model in the file application/models/Model_name.php. The class name and the file name should be capitalized and match each other. For example, if you want to create a User model, then you need to create a file named User.php in application/models folder with this code:
<?php defined('BASEPATH') OR exit('No direct script access allowed'); class User extends CI_Model public function __construct() parent::__construct(); // Load the database library here $this->load->database(); public function get_user($id) // This is a method that returns a user record by id // You can use the query builder class to create and execute SQL queries $query = $this->db->get_where('users', array('id' => $id)); return $query->row_array(); public function insert_user($data) // This is a method that inserts a new user record // You can use the query builder class to create and execute SQL queries return $this->db->insert('users', $data); public function update_user($id, $data) // This is a method that updates an existing user record // You can use the query builder class to create and execute SQL queries return $this->db->where('id', $id)->update('users', $data); public function delete_user($id) // This is a method that deletes a user record by id // You can use the query builder class to create and execute SQL queries return $this->db->delete('users', array('id' => $id)); // You can add more methods here as per your requirement
To load a model from a controller, you need to use the syntax $this->load->model('model_name'). For example, if you want to load the User model from the profile method of the Users controller, then you can use this code:
$this->load->model('user');
To call a model method, you need to use the syntax $this->model_name->method_name(). For example, if you want to call the get_user method of the User model from the profile method of the Users controller, then you can use this code:
$user = $this->user->get_user($id);
Libraries and Helpers
Libraries are classes that provide various functionalities for common web development tasks, such as database access, form validation, email sending, session management, image manipulation, and more. CodeIgniter 3 comes with a set of built-in libraries that are located in the system/libraries folder. You can also create your own custom libraries or use third-party libraries that are compatible with CodeIgniter 3.
Helpers are files that contain a collection of functions that perform specific tasks, such as working with arrays, strings, dates, URLs, forms, and more. CodeIgniter 3 comes with a set of built-in helpers that are located in the system/helpers folder. You can also create your own custom helpers or use third-party helpers that are compatible with CodeIgniter 3.
To load a library or a helper from a controller or a model, you need to use the syntax $this->load->library('library_name') or $this->load->helper('helper_name'). For example, if you want to load the email library and the url helper from the index method of the Users controller, then you can use this code:
$this->load->library('email'); $this->load->helper('url');
To call a library method or a helper function, you need to use the syntax $this->library_name->method_name() or function_name(). For example, if you want to send an email using the email library and redirect to another URL using the url helper from the index method of the Users controller, then you can use this code:
$this->email->from('your@example.com', 'Your Name'); $this->email->to('someone@example.com'); $this->email->subject('Email Test'); $this->email->message('This is a test email from CodeIgniter 3.'); $this->email->send(); redirect('users/profile'); >
Conclusion
In this article, we have learned how to download, install, and use CodeIgniter 3, a popular and powerful PHP framework that follows the MVC design pattern. We have also covered some of the main features, components, and concepts of CodeIgniter 3, such as routing, controllers, views, models, libraries, helpers, and more. CodeIgniter 3 is a great choice for developing dynamic web applications that are simple, fast, and secure.
FAQs
Here are some of the frequently asked questions about CodeIgniter 3:
Q: What is the difference between CodeIgniter 3 and CodeIgniter 4?
A: CodeIgniter 4 is the latest version of the framework that supports PHP 7.2 and above. It has a new codebase that is more modern, modular, and flexible. It also has some new features and improvements, such as namespaces, autoloading, dependency injection, filters, events, validation, testing, and more. However, CodeIgniter 4 is not backward compatible with CodeIgniter 3, so you need to rewrite your code if you want to migrate from CodeIgniter 3 to CodeIgniter 4.
Q: How can I learn more about CodeIgniter 3?
A: The best way to learn more about CodeIgniter 3 is to read the official documentation at . It covers all the aspects of the framework in detail and provides examples and tutorials. You can also check out some of the online courses, books, blogs, and forums that teach CodeIgniter 3.
Q: How can I get help or support for CodeIgniter 3?
A: You can get help or support for CodeIgniter 3 from the official community at . You can also ask questions on Stack Overflow or other platforms that have a tag for CodeIgniter 3.
Q: How can I contribute to CodeIgniter 3?
A: You can contribute to CodeIgniter 3 by reporting bugs, suggesting features, submitting patches, writing documentation, or creating extensions. You can find more information on how to contribute at .
Q: How can I stay updated with the latest news and developments of CodeIgniter 3?
A: You can stay updated with the latest news and developments of CodeIgniter 3 by following the official blog at .
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