CodeIgniter 4 How To Get Domain Name From Subdomain

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In web development, extracting domain names from subdomains is a common requirement, allowing applications to derive the main domain name from various subdomains.

In CodeIgniter 4, a powerful PHP framework, extracting domain names from subdomains enables developers to parse and utilize domain-related information effectively. In this tutorial, we’ll explore the process of extracting domain names from subdomains in CodeIgniter 4.

Read More: How To Work with CodeIgniter 4 Database Queries Tutorial




Let’s get started.

CodeIgniter 4 Installation

To create a CodeIgniter 4 setup run this given command into your shell or terminal. Please make sure composer should be installed.

composer create-project codeigniter4/appstarter codeigniter-4

Assuming you have successfully installed application into your local system.

Environment (.env) Setup

When we install CodeIgniter 4, we will have env file at root. To use the environment variables means using variables at global scope we need to do env to .env

Either we can do via renaming file as simple as that. Also we can do by terminal command.

Open project in terminal

cp env .env

Above command will create a copy of env file to .env file. Now we are ready to use environment variables.

Enable Development Mode

CodeIgniter starts up in production mode by default. You need to make it in development mode to see any error if you are working with application.

Open .env file from root.

# CI_ENVIRONMENT = production

 // Do it to 
CI_ENVIRONMENT = development

Now application is in development mode.

Create Custom Helper

Create a file inside /app/Helpers folder with name say custom_helper.php. Inside this naming convention, you can see we have used suffix as _helper.

Open custom_helper.php file and write following code into it.


// Get domain name from subdomain
// Example: =>

if (!function_exists('get_domain_from_subdomain')) {

    function get_domain_from_subdomain($subdomain)
        $pieces = parse_url($subdomain);
        $domain = isset($pieces['host']) ? $pieces['host'] : '';
        if (preg_match('/(?P<domain>[a-z0-9][a-z0-9\-]{1,63}\.[a-z\.]{2,6})$/i', $domain, $regs)) {
            return $regs['domain'];
        return false;

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Create Controller & Load Helper (Helper Usage)

To create a controller, run this command.

php spark make:controller SiteController

It will create SiteController.php inside /app/Controllers folder.

Open SiteController.php and write this complete code into it.


namespace App\Controllers;

use App\Controllers\BaseController;

class SiteController extends BaseController
	public function index()
		helper("custom"); // loading helper

		echo get_domain_from_subdomain("");


We used PHP functions parse_url() and preg_match() with regex pattern to remove https://, www., etc.

Add Route

Open Routes.php from /app/Config folder. Add this route into it.


$routes->get("domain-name", "SiteController::index");

Application Testing

Open project terminal and start development server via command:

php spark serve

URL: http://localhost:8080/domain-name

That’s it.

We hope this article helped you to learn about CodeIgniter 4 How To Get Domain Name From Subdomain Tutorial in a very detailed way.

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Sanjay KumarHello friends, I am Sanjay Kumar a Web Developer by profession. Additionally I'm also a Blogger, Youtuber by Passion. I founded Online Web Tutor and Skillshike platforms. By using these platforms I am sharing the valuable knowledge of Programming, Tips and Tricks, Programming Standards and more what I have with you all. Read more