How to Create RESTful APIs Using CodeIgniter

Introduction

CodeIgniter is a powerful PHP framework that is lightweight and easy to use, making it an excellent choice for developing RESTful APIs. In this guide, we will cover how to create a RESTful API using CodeIgniter, including setting up the environment, creating API routes, handling requests, and securing the API.

Prerequisites

Before you start, ensure you have the following:

• PHP 7.2 or later

• CodeIgniter 4 installed

• A MySQL database (optional, for data storage)

• Basic knowledge of PHP and CodeIgniter

Setting Up CodeIgniter

If you haven’t installed CodeIgniter yet, you can do so using Composer:

composer create-project codeigniter4/appstarter my_api_project
cd my_api_project

Enable .env File

Rename the .env.example file to .env and configure your database settings:

database.default.hostname = localhost
database.default.database = my_database
database.default.username = root
database.default.password = secret
database.default.DBDriver = MySQLi

Creating a RESTful Controller

CodeIgniter provides a ResourceController that simplifies API development. Create a new controller:

php spark make:controller StudentController --resource

This generates StudentController.php in app/Controllers/ with pre-defined CRUD methods.

Define API Routes

Modify app/Config/Routes.php to add API routes:

$routes->resource('students');

This automatically maps CRUD operations to the corresponding API endpoints:

• GET /students – Fetch all students

• POST /students – Create a new student

• GET /students/{id} – Fetch a single student

• PUT /students/{id} – Update a student

• DELETE /students/{id} – Delete a student

Implementing API Logic

Edit app/Controllers/StudentController.php to handle requests.

Define Model

Create a model StudentModel.php in app/Models/:

namespace App\Models;

use CodeIgniter\Model;

class StudentModel extends Model
{
    protected $table = 'students';
    protected $primaryKey = 'id';
    protected $allowedFields = ['name', 'email', 'age'];
}

Implement Controller Methods

Edit StudentController.php:

namespace App\Controllers;

use App\Models\StudentModel;
use CodeIgniter\RESTful\ResourceController;

class StudentController extends ResourceController
{
    protected $modelName = 'App\Models\StudentModel';
    protected $format = 'json';

    public function index()
    {
        return $this->respond($this->model->findAll());
    }

    public function show($id = null)
    {
        $student = $this->model->find($id);
        return $student ? $this->respond($student) : $this->failNotFound('Student not found');
    }

    public function create()
    {
        $data = $this->request->getPost();
        if ($this->model->insert($data)) {
            return $this->respondCreated($data);
        }
        return $this->failValidationErrors('Invalid data');
    }

    public function update($id = null)
    {
        $data = $this->request->getRawInput();
        if ($this->model->update($id, $data)) {
            return $this->respondUpdated($data);
        }
        return $this->failNotFound('Student not found');
    }

    public function delete($id = null)
    {
        if ($this->model->delete($id)) {
            return $this->respondDeleted(['message' => 'Student deleted']);
        }
        return $this->failNotFound('Student not found');
    }
}

Testing the API

Use Postman or cURL to test the endpoints.

Fetch All Students

curl -X GET http://localhost:8080/students

Create a New Student

curl -X POST http://localhost:8080/students -d "name=John Doe&email=john@example.com&age=22"

Update a Student

curl -X PUT http://localhost:8080/students/1 -d "name=Updated Name"

Delete a Student

curl -X DELETE http://localhost:8080/students/1

Securing the API

To secure the API, implement authentication and validation:

Authentication with API Key

Modify app/Filters/ApiAuthFilter.php:

namespace App\Filters;

use CodeIgniter\HTTP\RequestInterface;
use CodeIgniter\HTTP\ResponseInterface;
use CodeIgniter\Filters\FilterInterface;

class ApiAuthFilter implements FilterInterface
{
    public function before(RequestInterface $request, $arguments = null)
    {
        $apiKey = $request->getHeaderLine('X-API-KEY');
        if ($apiKey !== 'your_secret_api_key') {
            return service('response')->setJSON(['message' => 'Unauthorized'])->setStatusCode(401);
        }
    }

    public function after(RequestInterface $request, ResponseInterface $response, $arguments = null)
    {
        // Optional post-processing
    }
}

Enable the filter in app/Config/Filters.php:

public $aliases = [
    'apiauth' => \App\Filters\ApiAuthFilter::class,
];

Apply it to routes:

$routes->group('students', ['filter' => 'apiauth'], function ($routes) {
    $routes->resource('students');
});

Conclusion

You have now created a RESTful API using CodeIgniter, complete with CRUD operations and API authentication. This setup can be extended further with features like JWT authentication, rate limiting, and versioning to enhance security and performance.