Working with REST API in OpenCart 4

OpenCart 4 has a built-in REST API that allows you to integrate the store with external systems: mobile apps, CRM, ERP, and other services.

API Setup

To start working with the API, you need to:

1. Enable API in admin panel: System → Users → API
2. Create an API user
3. Generate API key
4. Configure allowed IPs (optional)

Authentication

OpenCart 4 uses token-based authentication:

// Getting token
$curl = curl_init();
curl_setopt_array($curl, [
    CURLOPT_URL => 'https://your-store.com/index.php?route=api/account/login',
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_POST => true,
    CURLOPT_POSTFIELDS => [
        'username' => 'api_user',
        'key' => 'your_api_key'
    ]
]);

$response = curl_exec($curl);
$data = json_decode($response, true);
$token = $data['api_token'];

Main Endpoints

Products

// Get product list
GET /index.php?route=api/product&api_token={token}

// Get single product
GET /index.php?route=api/product&api_token={token}&product_id=123

// Search products
GET /index.php?route=api/product&api_token={token}&search=laptop

Cart

// Add product to cart
POST /index.php?route=api/cart/add&api_token={token}
{
    "product_id": 123,
    "quantity": 2,
    "option": {
        "226": "red"
    }
}

// Get cart contents
GET /index.php?route=api/cart/products&api_token={token}

// Remove from cart
POST /index.php?route=api/cart/remove&api_token={token}
{
    "key": "cart_item_key"
}

Orders

// Create order
POST /index.php?route=api/order/add&api_token={token}
{
    "customer_id": 1,
    "payment_address": {...},
    "shipping_address": {...},
    "payment_method": "cod",
    "shipping_method": "flat.flat"
}

// Order history
GET /index.php?route=api/order/history&api_token={token}&order_id=100

API is a contract between systems. Document all endpoints and version your API for backward compatibility.

— Best Practice

Creating Custom API Endpoint

<?php
// catalog/controller/api/custom.php
namespace Opencart\Catalog\Controller\Api;

class Custom extends \Opencart\System\Engine\Controller {
    public function index(): void {
        $this->load->language('api/custom');

        $json = [];

        if (!isset($this->session->data['api_id'])) {
            $json['error'] = 'Unauthorized';
        } else {
            // Your logic
            $json['success'] = true;
            $json['data'] = [
                'message' => 'Custom API works!'
            ];
        }

        $this->response->addHeader('Content-Type: application/json');
        $this->response->setOutput(json_encode($json));
    }
}

Error Handling

// Standard response structure
{
    "success": true,
    "data": {...}
}

// Error
{
    "error": "Product not found",
    "error_code": 404
}

Example: Mobile App

// JavaScript/React Native example
const API_URL = 'https://your-store.com/index.php';
let apiToken = null;

async function login() {
    const response = await fetch(`${API_URL}?route=api/account/login`, {
        method: 'POST',
        body: JSON.stringify({
            username: 'api_user',
            key: 'api_key'
        })
    });
    const data = await response.json();
    apiToken = data.api_token;
}

async function getProducts() {
    const response = await fetch(
        `${API_URL}?route=api/product&api_token=${apiToken}`
    );
    return response.json();
}

Conclusion

REST API opens many possibilities for integrating OpenCart with other systems. Start by learning the built-in endpoints, then create your own for your business's specific needs.