Codeigniter 4: Creating Your First REST API Endpoint in CodeIgniter

Building a REST API in CodeIgniter starts with creating endpoints to handle client requests. In this guide, we will demonstrate how to create a simple “Hello World” REST API endpoint.

Step 1: Set Up a Controller

CodeIgniter organizes its logic into controllers. Start by creating a controller for your API:

1. Navigate to the app/Controllers directory.
2. Create a new file named HelloController.php.
3. Add the following code to define the controller:

namespace App\Controllers;

use CodeIgniter\RESTful\ResourceController;

class HelloController extends ResourceController {
    public function index() {
        return $this->respond([
            'message' => 'Hello, World! Welcome to CodeIgniter REST API.'
        ]);
    }
}

Step 2: Define a Route

Routes map URL requests to specific controller methods. Add a route for your endpoint in the app/Config/Routes.php file:

$routes->get('hello', 'HelloController::index');

Step 3: Test Your Endpoint

1. Start your development server:

   php spark serve

2. Open your browser or use a tool like Postman to send a GET request to:

   http://localhost:8080/hello

3. You should see the following JSON response:

   {
       "message": "Hello, World! Welcome to CodeIgniter REST API."
   }

Step 4: Expand Functionality

To add more endpoints, create additional methods in your controller and define corresponding routes. For instance, to create a greet method:

public function greet($name) {
    return $this->respond([
        'message' => "Hello, $name! Welcome to CodeIgniter REST API."
    ]);
}

Add the route:

$routes->get('hello/greet/(:any)', 'HelloController::greet/$1');

Conclusion

Congratulations! You have created your first REST API endpoint in CodeIgniter. This simple example can serve as a foundation for more complex APIs. In the next blog, we’ll discuss handling CRUD operations in a REST API.