Klarna Payment Gateway Integration in PHP

Payment gateways are a crucial component of e-commerce websites, allowing businesses to accept online payments securely and efficiently. Klarna, a popular payment service provider, offers a range of payment solutions that enable customers to make purchases with ease. In this article, we will explore the process of integrating Klarna payment gateway into a PHP-based e-commerce website. Klarna payment gateway integration into a PHP application involves several steps, including setting up your Klarna account, obtaining API credentials, and implementing the necessary code in your PHP application. Here’s an example of Klarna payment gateway integration in PHP.

Klarna Payment Gateway Integration Prerequisites

Before you begin the integration process, you need to have a few things in place:

Klarna Account: You must have a Klarna business account. If you don’t have one, you can sign up on the Klarna website.
API Credentials: Klarna provides API credentials, including a merchant ID, shared secret, and base URL. You can obtain these credentials by contacting Klarna’s support or through the Klarna Merchant Portal.
SSL Certificate: Ensure that your website has a valid SSL certificate for secure communication with Klarna’s servers. This is essential to protect customer data during the checkout process.

Step 1: Set Up a Klarna Account
Before you can integrate Klarna into your PHP website, you need to create an account with Klarna. Visit the Klarna website and sign up for an account. Once you’ve created your account, you’ll have access to the Klarna Merchant Portal, where you can obtain your API credentials and configure your payment options.
Step 2: Obtain API Credentials
To interact with Klarna’s API, you’ll need API credentials, which include the Merchant ID and API Secret. You can find these credentials in the Klarna Merchant Portal. Here’s how you can obtain them:
- Log in to your Klarna Merchant Portal.
- Navigate to the “Settings” or “Integration” section.
- Find the API credentials, which may be labeled as “Merchant ID” and “API Secret.”
- Note down these credentials as you will need them for the integration process.
Step 3: Install Klarna PHP SDK
To make the integration process smoother, Klarna provides an official PHP SDK (Software Development Kit). You can use Composer to install the SDK in your project. If you don’t have Composer installed, you can download and install it from the official Composer website. To install the Klarna PHP SDK, open your project’s terminal and run the following command:
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Syntax Highlightercomposer require klarna/kco
This command will download and install the Klarna PHP SDK into your project.
Step 4: Configure the SDK
After installing the Klarna PHP SDK, you need to configure it with your API credentials. Open the configuration file provided by the SDK, which is usually named config.php or something similar. Update the configuration with your Merchant ID and API Secret.
Here’s an example of what your config.php might look like:
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Syntax Highlighter<?php define('KLARNA_MERCHANT_ID', 'your_merchant_id'); define('KLARNA_SHARED_SECRET', 'your_shared_secret');
Make sure to replace 'your_merchant_id' and 'your_shared_secret' with your actual API credentials.
Step 5: Create a Klarna Payment Function
In your PHP application, you should create a function that initializes the Klarna payment process. This function will interact with the Klarna API to create a new order. Here’s a basic example of how this function might look:
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Syntax Highlighter<?php require 'config.php'; require 'vendor/autoload.php'; // Composer autoloader use Klarna\Rest\Transport\Connector; use Klarna\Rest\Checkout\Order; use Klarna\Rest\Checkout\Cart; function createKlarnaPayment() { $connector = Connector::create($klarnaConfig); // Create a new order $order = new Order($connector); $order->fetch(); // Create a cart $cart = new Cart(); // Add products to the cart // Set the merchant URLs (success, cancel, etc.) $order->merchant_urls->set_url('success', 'https://yourwebsite.com/success'); $order->merchant_urls->set_url('cancel', 'https://yourwebsite.com/cancel'); // Set the purchase country, currency, and locale $order->purchase_country = 'US'; $order->purchase_currency = 'USD'; $order->locale = 'en-US'; // Initialize the order $order->create($cart); // Redirect to the Klarna checkout header('Location: ' . $order['gui']['redirect_url']); }
This function initializes a Klarna order, adds products to a cart, and sets the merchant URLs. Finally, it redirects the user to the Klarna checkout page.
Step 6: Handle the Klarna Callback
After the customer completes the payment on the Klarna checkout page, Klarna will send callback data to your server. Create an endpoint in your custom PHP website that handles these callbacks. Here’s a basic example of how you can handle a Klarna callback:
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Syntax Highlighter<?php require 'klarna-config.php'; require 'vendor/autoload.php'; // Composer autoloader use Klarna\Rest\Transport\Connector; use Klarna\Rest\Checkout\Order; // Initialize the Klarna connector $klarnaConfig = [ 'merchant_id' => KLARNA_MERCHANT_ID, 'shared_secret' => KLARNA_SHARED_SECRET, 'base_url' => 'https://yourwebsite.com', // Replace with your website's URL ]; $connector = Connector::create($klarnaConfig); // Initialize the Klarna order $order = new Order($connector); // Handle the callback if ($order->fetch()) { $status = $order['status']; // Process the order status switch ($status) { case 'checkout_incomplete': // Handle incomplete checkout break; case 'checkout_complete': // Handle successful checkout break; // Add more cases for different order statuses as needed } }
This code handles the callback from Klarna, checks the order status, and processes it accordingly.
Step 7: Testing the Integration
Before going live, it’s essential to conduct comprehensive testing of your Klarna integration. Klarna provides a test environment that allows you to simulate various scenarios, including successful payments, failed payments, and different order statuses. Be sure to test different payment methods, including Pay Now, Pay Later, Slice It, and Financing.
Step 8: Going Live
Once you are satisfied with the testing and everything is working as expected, you can switch to the production environment by updating your Klarna API credentials to use the live merchant ID and shared secret. Ensure that you also update your website’s live URL in the Klarna configuration.

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