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Architecture of CodeIgniter

CodeIgniter is a powerful PHP framework that follows the Model-View-Controller (MVC) architectural pattern. MVC is a popular design pattern used in web application development to separate the application logic, presentation, and data. In this pattern, the application is divided into three main components: Model, View, and Controller.

Model

The Model represents the application's data and business logic. It interacts with the database or any other data storage system to retrieve and store data. The Model is responsible for processing data and performing any necessary validations before passing it to the Controller. In CodeIgniter, Models are defined as classes and are saved in the application/models directory.

View

The View is responsible for presenting the data to the user in a format that can be easily understood. It interacts with the Model to retrieve data and then formats it for presentation. Views in CodeIgniter are HTML files that are saved in the application/views directory.

Controller

The Controller handles user requests and controls the flow of data between the Model and View. It receives input from the user via the View, processes it, and then instructs the Model to retrieve and modify data as necessary. The Controller then formats the data and passes it to the View for display. Controllers in CodeIgniter are classes and are saved in the application/controllers directory.

Example

Consider the following example of a simple CodeIgniter application that displays a list of products:

/controllers/Products.php

class Products extends CI_Controller {
    public function index() {
        $this->load->model('Product_model');
        $data['products'] = $this->Product_model->get_products();
        $this->load->view('product_list', $data);
    }
}

/models/Product_model.php

class Product_model extends CI_Model {
    public function get_products() {
        $query = $this->db->get('products');
        return $query->result();
    }
}

/views/product_list.php

<html>
<head>
    <title>Product List</title>
</head>
<body>
    <ul>
        <?php foreach ($products as $product): ?>
            <li><?php echo $product->name ?></li>
        <?php endforeach; ?>
    </ul>
</body>
</html>

In this example, the Controller (Products.php) handles the user request and loads the Model (Product_model.php) to retrieve the list of products from the database. The Controller then loads the View (product_list.php) to display the products in an HTML list format.

Explanation

In this example, the user requests the list of products by visiting the URL that maps to the Products Controller. The index() function in the Products Controller loads the Product_model to retrieve the list of products from the database. The Controller then loads the product_list View to display the products using an HTML unordered list (ul) and loop through the retrieved products data to display each product name in an HTML list item (li).

Use

The MVC architectural pattern in CodeIgniter is used to separate the application logic, presentation, and data, providing developers with an organized, maintainable, and scalable code base. With MVC, developers can add new features, change existing features, and fix bugs without affecting the rest of the application. In addition, MVC allows for easy unit testing and promotes code reusability.

Important Points

  • CodeIgniter follows the Model-View-Controller (MVC) architectural pattern.
  • The Model represents the application's data and business logic.
  • The View is responsible for displaying the data to the user in a format that can be easily understood.
  • The Controller receives user requests, processes user input, and communicates with the Model and View to generate the appropriate output.
  • MVC pattern in CodeIgniter enables developers with an organized, scalable code base, easier maintenance & updates.

Summary

CodeIgniter is a powerful PHP framework that follows the Model-View-Controller architectural pattern. In CodeIgniter, Models, Views, and Controllers are the three main components of the MVC architecture. Models are responsible for managing data, Views display data to the user, and Controllers handle user input, interact with the Model and View to generate the appropriate output. MVC pattern in CodeIgniter makes a well-defined architecture and promotes reusability, making developers work more systematically & efficiently.

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