PayPal provides an easy way to integrate a standard payment gateway in PHP. If your web application is built with CodeIgniter 4, the PayPal PHP library and API need to be integrated into the CodeIgniter 4 application. 

This tutorial will guide you through integrating PayPal payment processing into a CodeIgniter 4 application. We’ll create a simple example to demonstrate the process.

Prerequisites

1. Basic knowledge of PHP and CodeIgniter 4.
2. A CodeIgniter 4 project set up.
3. A PayPal Developer account.

Set Up Your CodeIgniter 4 Project & Install PayPal SDK via Composer

Ensure you have CodeIgniter 4 installed.

composer require paypal/paypal-checkout-sdk

Create a PayPal Developer Account

1. Visit the PayPal Developer Portal.
2. Log in or create an account.
3. Create a new app under the “My Apps & Credentials” section to get your Client ID and Secret.

Configure CodeIgniter for PayPal

$clientId = 'ARF2P04R0r_x_fQ-fATDzXXXXXXX7hCy1eMxymIYYQQ5zR-0QzKPpFGhTH6vDVMG';
$clientSecret = 'EB-Gy0qyz1JbQJoAM1QNXXXXXXXXXXXXXq2fNCI0Ir92UsRO3TlSJ5Wmne9aM-cJqGopgIHK0Ec1';

Create a Controller for PayPal Integration

Create a new controller app/Controllers/payment/Paypal.php:

<?php
namespace App\Controllers\payment;
use App\Controllers\BaseController;

use PayPalCheckoutSdk\Core\PayPalHttpClient;
use PayPalCheckoutSdk\Core\SandboxEnvironment;
use PayPalCheckoutSdk\Core\ProductionEnvironment;
use PayPalCheckoutSdk\Orders\OrdersCreateRequest;
use PayPalCheckoutSdk\Orders\OrdersCaptureRequest;

class Paypal extends BaseController {

    public function __construct() {
        $db = db_connect();

        $this->ip_address               = $_SERVER['REMOTE_ADDR'];
        $this->datetime                 = date("Y-m-d H:i:s");
    }

    public function index() {
        $data                       = [];
        $data ['content_title']     = 'Pay with Paypal using CodeIgniter 4';
        echo view('home', $data);
    }

    public function create() {
        $amount         = $this->request->getGet('amount');
        $currency       = $this->request->getGet('currency');
        $clientId       = 'ARF2P04R0r_x_fQ-fATDz7AqlyFY1Vpqk9Gu2uXCzk9R7hCy1eMxymIYYQQ5zR-0QzKPpFGhTH6vDVMG';
        $clientSecret   = 'EB-Gy0qyz1JbQJoAM1QNmX_ld0G8HNA8BIkkVq2fNCI0Ir92UsRO3TlSJ5Wmne9aM-cJqGopgIHK0Ec1';
        $paypal_sandbox = true;
        if ($paypal_sandbox) {
            $environment = new SandboxEnvironment($clientId, $clientSecret);
        } else {
            $environment = new ProductionEnvironment($clientId, $clientSecret);
        }
        $client = new PayPalHttpClient($environment);
        $request = new OrdersCreateRequest();
        $request->prefer('return=representation');

        $request->body = [
                "intent"            => "CAPTURE",
                "purchase_units"    => [[
        "reference_id" => rand(000000,999999),
                "amount" => [
        "value"             => number_format($amount, 2, '.', ''),
                "currency_code"     => $currency,
            ]
        ]],
        "application_context" => [
        "cancel_url" => base_url('payment/paypal/cancel'),
                "return_url" => base_url('payment/paypal/complete')
        ]
    ];

        try {
            // Call API with your client and get a response for your call
            $response = $client->execute($request);
            // If call returns body in response, you can get the deserialized version from the result attribute of the response
            return redirect()->to($response->result->links[1]->href);
        } catch (HttpException $ex) {
            echo $ex->statusCode;
            print_r($ex->getMessage());
        }
    }

    public function cancel() {
        $token          = $this->request->getGet('token');
        echo 'Payment has been failed';
    }

    public function complete() {
        $order_id       = $this->request->getGet('order_id');
        $token          = $this->request->getGet('token');
        $clientId       = 'ARF2P04R0r_x_fQ-fATDz7AqlyFY1Vpqk9Gu2uXCzk9R7hCy1eMxymIYYQQ5zR-0QzKPpFGhTH6vDVMG';
        $clientSecret   = 'EB-Gy0qyz1JbQJoAM1QNmX_ld0G8HNA8BIkkVq2fNCI0Ir92UsRO3TlSJ5Wmne9aM-cJqGopgIHK0Ec1';
        $paypal_sandbox = true;
        if ($paypal_sandbox) {
            $environment = new SandboxEnvironment($clientId, $clientSecret);
        } else {
            $environment = new ProductionEnvironment($clientId, $clientSecret);
        }
        $client     = new PayPalHttpClient($environment);
        $request    = new OrdersCaptureRequest($token);
        $request->prefer('return=representation');

        try {
            // Call API with your client and get a response for your call
            $response = $client->execute($request);
            // If call returns body in response, you can get the deserialized version from the result attribute of the response
            print_r($response);
            echo 'Paid successfully';
        } catch (HttpException $ex) {
            // echo $ex->statusCode;
            print_r($ex->getMessage());
        }
    }
}

Define Routes

Add routes for the PayPal controller in app/Config/Routes.php:

$routes->get('/', 'Home::index');

$routes->group('payment', function($routes) {
    $routes->group('paypal', function($routes) {
        $routes->get('/',           'payment\Paypal::index');
        $routes->get('create',      'payment\Paypal::create');
        $routes->post('create',     'payment\Paypal::create');
        $routes->get('cancel',      'payment\Paypal::cancel');
        $routes->get('complete',    'payment\Paypal::complete');
    });
});

Create a View for Payment

Create a simple view app/Views/home.php:

<!DOCTYPE html>
<html lang="en">

<head>
   <title><?php echo $content_title; ?></title>
   <meta charset="utf-8">
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@4.6.2/dist/css/bootstrap.min.css">
   <script src="https://cdn.jsdelivr.net/npm/jquery@3.7.1/dist/jquery.slim.min.js"></script>
   <script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.1/dist/umd/popper.min.js"></script>
   <script src="https://cdn.jsdelivr.net/npm/bootstrap@4.6.2/dist/js/bootstrap.bundle.min.js"></script>
</head>

<body>

   <div class="container mt-5">
      <div class="jumbotron text-center">
    <h1>Pay with <img src="<?php echo base_url('images/paypal.png'); ?>" class="img img-fluid" width="150px"> using CodeIgniter 4</h1>
    <p>By infovistar.in</p>
      </div>
      <div class="row">
         <div class="col-sm-3">
         </div>
         <div class="col-sm-6">
            <form method="get" action="<?php echo base_url('payment/paypal/create'); ?>" autocomplete="off">
               <div class="form-group">
                  <label>Amount</label>
                  <input type="number" name="amount" min="1" value="1" class="form-control">
               </div>
               <div class="form-group">
                  <label>Currency</label>
                  <input type="text" name="currency" value="USD" class="form-control" readonly>
               </div>
               <div class="form-group">
                  <button type="submit" class="btn btn-primary">Pay</button>
               </div>
            </form>
         </div>
         <div class="col-sm-3">
         </div>
      </div>
   </div>
</body>

</html>

Test the Integration

Run your CodeIgniter application:

php spark serve

Navigate to http://localhost:8080 and click the “Pay Now” button to start the PayPal payment process.

This simple tutorial demonstrates how to integrate PayPal payments into a CodeIgniter 4 application. You can further enhance the example by adding error handling, logging, and other necessary features for a production environment.