How to use CodeIgniter 3 with PHP programming?

As the Internet continues to develop, the development of modern websites and web applications has become increasingly complex. Writing large, complex applications often requires experienced developers and can take a lot of time and cost. However, the emergence of modern PHP frameworks can help developers build complex applications more quickly while improving productivity and code quality. Among them, CodeIgniter is a popular PHP framework that is widely used in the development of web applications.

This article will introduce some basic knowledge and code demonstrations of the CodeIgniter 3 framework, allowing you to quickly get started and use CodeIgniter to implement your web application.

What is CodeIgniter?

CodeIgniter is a lightweight PHP framework released by EllisLab in 2006. It is free software and developers can modify and customize it according to their needs. CodeIgniter has many advantages, the most important of which are speed, lightweight and flexibility. CodeIgniter is widely used in web development and backend development of mobile applications. CodeIgniter's API is very simple to use, easy to learn and extensible.

How to install CodeIgniter?

Download the latest version of CodeIgniter 3, unzip it and place it in the root directory of your web server. Open your web browser and type your website address. If you have successfully installed the CodeIgniter framework, you will see the CodeIgniter welcome page.

The directory structure of the CodeIgniter framework

The directory structure of the CodeIgniter framework is as follows:

/application
/system
/index.php
/.htaccess

There are two important directories here, namely /application and /system. The

/application directory contains your application code and resources. Your core application code should be located in /application/controllers, /application/models, /application/views, etc. directories. The

/system directory contains all core components of the CodeIgniter framework. You usually do not need to modify these files.

How to configure CodeIgniter?

CodeIgniter’s configuration file is located at /application/config/config.php. You can open this file and find the settings you need to change. For example, if you want CodeIgniter to use HTTPS instead of HTTP, you can change the following line:

$config['base_url'] = 'https://example.com';

Another important configuration file is the /database.php file. You can set your database connection information in this file.

How to create a controller?

The controller is an important component in CodeIgniter, which is used to process user requests and return responses. You can create a controller by inheriting CodeIgniter's CI_Controller class. For example, to create a controller called "Welcome", you would create a file called "application/controllers/Welcome.php" and write the following code:

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Welcome extends CI_Controller {

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

In this code, we A controller named "Welcome" is defined and a handler method named "index" is created. This handler loads the view "welcome_message". Your controller can return responses, load models, and perform other operations.

How to create a model?

The model is an important component in CodeIgniter for interacting with the database. To create a model, you need to create a file called "models/Example_model.php" and write the following code:

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Example_model extends CI_Model {

    public function get_data()
    {
        return array(
            'title' => 'Hello, World!',
            'content' => 'This is an example article.'
        );
    }

}

In this code, we define a model called "Example_model", And created a processing method called "get_data". This handler returns an array containing "title" and "content". You can use models to query a database and return data.

How to create a view?

View is a template engine component in CodeIgniter, used to create dynamic HTML interfaces. To create a view, you need to create a file and place it in the "views/" directory. For example, to create a view file named "welcome_message.php", you can write the following code:

<!DOCTYPE html>
<html>
<head>
    <title><?php echo $title; ?></title>
</head>
<body>

    <h1><?php echo $title; ?></h1>
    <p><?php echo $content; ?></p>

</body>
</html>

In this code, we have created the HTML code and embedded the PHP tag for displaying the view from the control The data returned by the processor and model.

How to load the view?

To load a view in a controller, you can use the "load->view()" function. For example, to load a view named "welcome_message" in the controller above, you would add the following code to the "index" method:

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Welcome extends CI_Controller {

    public function index()
    {
        $this->load->model('example_model');
        $data = $this->example_model->get_data();

        $this->load->view('welcome_message', $data);
    }
}

In this code, we loaded the view from "example_model" data, passed it to the "view" function, and passed it along with the "welcome_message" view file.

Summary

This article introduces some basic knowledge and code demonstrations of the CodeIgniter framework, including framework installation, directory structure, configuration, controllers, models and views. CodeIgniter has a very simple and easy-to-use API and fast and flexible performance to help you write the backend of web applications and mobile applications faster. I hope this article can help you better understand and use the CodeIgniter framework.

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