Developing Payment Gateways

Create custom payment gateway extensions for OpenCart with complete implementation examples

Overview

Payment gateways process customer payments during checkout. They require both admin configuration and catalog payment processing logic.

Payment Gateway Structure

extension/myvendor/
├── admin/
│   ├── controller/payment/mypayment.php
│   ├── language/en-gb/payment/mypayment.php
│   └── view/template/payment/mypayment.twig
└── catalog/
    ├── controller/payment/mypayment.php
    └── language/en-gb/payment/mypayment.php

Admin Controller

From admin/controller/extension/opencart/payment/bank_transfer.php:8:

<?php
namespace Opencart\Admin\Controller\Extension\Opencart\Payment;

class BankTransfer extends \Opencart\System\Engine\Controller {
    public function index(): void {
        $this->load->language('extension/opencart/payment/bank_transfer');
        
        $this->document->setTitle($this->language->get('heading_title'));
        
        $data['breadcrumbs'] = [];
        
        $data['breadcrumbs'][] = [
            'text' => $this->language->get('text_home'),
            'href' => $this->url->link('common/dashboard', 'user_token=' . $this->session->data['user_token'])
        ];
        
        $data['save'] = $this->url->link('extension/opencart/payment/bank_transfer.save', 'user_token=' . $this->session->data['user_token']);
        $data['back'] = $this->url->link('marketplace/extension', 'user_token=' . $this->session->data['user_token'] . '&type=payment');
        
        // Load configuration
        $data['payment_bank_transfer_status'] = $this->config->get('payment_bank_transfer_status');
        $data['payment_bank_transfer_sort_order'] = $this->config->get('payment_bank_transfer_sort_order');
        
        // Load order statuses
        $this->load->model('localisation/order_status');
        $data['order_statuses'] = $this->model_localisation_order_status->getOrderStatuses();
        
        // Load geo zones
        $this->load->model('localisation/geo_zone');
        $data['geo_zones'] = $this->model_localisation_geo_zone->getGeoZones();
        
        $this->response->setOutput($this->load->view('extension/opencart/payment/bank_transfer', $data));
    }
    
    public function save(): void {
        $this->load->language('extension/opencart/payment/bank_transfer');
        
        $json = [];
        
        if (!$this->user->hasPermission('modify', 'extension/opencart/payment/bank_transfer')) {
            $json['error']['warning'] = $this->language->get('error_permission');
        }
        
        if (!$json) {
            $this->load->model('setting/setting');
            $this->model_setting_setting->editSetting('payment_bank_transfer', $this->request->post);
            
            $json['success'] = $this->language->get('text_success');
        }
        
        $this->response->addHeader('Content-Type: application/json');
        $this->response->setOutput(json_encode($json));
    }
}

Catalog Controller

From catalog/controller/extension/opencart/payment/bank_transfer.php:8:

<?php
namespace Opencart\Catalog\Controller\Extension\Opencart\Payment;

class BankTransfer extends \Opencart\System\Engine\Controller {
    /**
     * Index - Display payment method
     *
     * @return string
     */
    public function index(): string {
        $this->load->language('extension/opencart/payment/bank_transfer');
        
        $data['bank'] = nl2br($this->config->get('payment_bank_transfer_bank_' . $this->config->get('config_language_id')));
        $data['language'] = $this->config->get('config_language');
        
        return $this->load->view('extension/opencart/payment/bank_transfer', $data);
    }
    
    /**
     * Confirm - Process payment
     *
     * @return void
     */
    public function confirm(): void {
        $this->load->language('extension/opencart/payment/bank_transfer');
        
        $json = [];
        
        if (!isset($this->session->data['order_id'])) {
            $json['error'] = $this->language->get('error_order');
        }
        
        // Validate order
        if (isset($this->session->data['order_id'])) {
            $this->load->model('checkout/order');
            
            $order_info = $this->model_checkout_order->getOrder($this->session->data['order_id']);
            
            if (!$order_info) {
                $json['redirect'] = $this->url->link('checkout/failure', 'language=' . $this->config->get('config_language'), true);
                unset($this->session->data['order_id']);
            }
        }
        
        // Validate payment method
        if (!isset($this->session->data['payment_method']) || 
            $this->session->data['payment_method']['code'] != 'bank_transfer.bank_transfer') {
            $json['error'] = $this->language->get('error_payment_method');
        }
        
        if (!$json) {
            // Add order history
            $comment  = $this->language->get('text_instruction') . "\n\n";
            $comment .= $this->config->get('payment_bank_transfer_bank_' . $this->config->get('config_language_id')) . "\n\n";
            $comment .= $this->language->get('text_payment');
            
            $this->load->model('checkout/order');
            
            $this->model_checkout_order->addHistory(
                $this->session->data['order_id'],
                $this->config->get('payment_bank_transfer_order_status_id'),
                $comment,
                true
            );
            
            $json['redirect'] = $this->url->link('checkout/success', 'language=' . $this->config->get('config_language'), true);
        }
        
        $this->response->addHeader('Content-Type: application/json');
        $this->response->setOutput(json_encode($json));
    }
}

Required Methods

index()

Display payment method information at checkout:

public function index(): string {
    $this->load->language('extension/myvendor/payment/mypayment');
    
    $data['api_key'] = $this->config->get('payment_mypayment_api_key');
    $data['button_confirm'] = $this->language->get('button_confirm');
    
    return $this->load->view('extension/myvendor/payment/mypayment', $data);
}

confirm()

Process the payment:

public function confirm(): void {
    $json = [];
    
    if (!isset($this->session->data['order_id'])) {
        $json['error'] = 'Order not found';
    }
    
    if (!$json) {
        // Process payment with API
        $result = $this->processPayment($this->session->data['order_id']);
        
        if ($result['success']) {
            $this->load->model('checkout/order');
            $this->model_checkout_order->addHistory(
                $this->session->data['order_id'],
                $this->config->get('payment_mypayment_order_status_id'),
                'Payment processed',
                true
            );
            
            $json['redirect'] = $this->url->link('checkout/success');
        } else {
            $json['error'] = $result['error'];
        }
    }
    
    $this->response->addHeader('Content-Type: application/json');
    $this->response->setOutput(json_encode($json));
}

Payment API Integration

API Request Example

private function processPayment(int $order_id): array {
    $this->load->model('checkout/order');
    $order_info = $this->model_checkout_order->getOrder($order_id);
    
    // Prepare API request
    $data = [
        'amount'      => $order_info['total'],
        'currency'    => $order_info['currency_code'],
        'order_id'    => $order_id,
        'return_url'  => $this->url->link('extension/myvendor/payment/mypayment.callback'),
        'cancel_url'  => $this->url->link('checkout/checkout')
    ];
    
    $curl = curl_init();
    
    curl_setopt($curl, CURLOPT_URL, 'https://api.paymentgateway.com/process');
    curl_setopt($curl, CURLOPT_POST, true);
    curl_setopt($curl, CURLOPT_POSTFIELDS, http_build_query($data));
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($curl, CURLOPT_HTTPHEADER, [
        'Authorization: Bearer ' . $this->config->get('payment_mypayment_api_key')
    ]);
    
    $response = curl_exec($curl);
    $http_code = curl_getinfo($curl, CURLINFO_HTTP_CODE);
    
    curl_close($curl);
    
    $result = json_decode($response, true);
    
    if ($http_code == 200 && isset($result['transaction_id'])) {
        return [
            'success' => true,
            'transaction_id' => $result['transaction_id']
        ];
    } else {
        return [
            'success' => false,
            'error' => $result['error'] ?? 'Payment failed'
        ];
    }
}

Callback Handler

public function callback(): void {
    // Validate callback
    $transaction_id = $this->request->get['transaction_id'] ?? '';
    $order_id = $this->request->get['order_id'] ?? 0;
    
    if (!$transaction_id || !$order_id) {
        $this->response->redirect($this->url->link('checkout/failure'));
        return;
    }
    
    // Verify with payment gateway
    $verified = $this->verifyTransaction($transaction_id);
    
    if ($verified) {
        $this->load->model('checkout/order');
        $this->model_checkout_order->addHistory(
            $order_id,
            $this->config->get('payment_mypayment_completed_status_id'),
            'Payment verified: ' . $transaction_id,
            true
        );
        
        $this->response->redirect($this->url->link('checkout/success'));
    } else {
        $this->response->redirect($this->url->link('checkout/failure'));
    }
}

Configuration Settings

Store API credentials and settings:

// Settings to save
$settings = [
    'payment_mypayment_api_key'              => 'YOUR_API_KEY',
    'payment_mypayment_api_secret'           => 'YOUR_SECRET',
    'payment_mypayment_test_mode'            => 1,
    'payment_mypayment_order_status_id'      => 1,
    'payment_mypayment_completed_status_id'  => 5,
    'payment_mypayment_geo_zone_id'          => 0,
    'payment_mypayment_status'               => 1,
    'payment_mypayment_sort_order'           => 1
];

$this->model_setting_setting->editSetting('payment_mypayment', $settings);

Next Steps

Shipping Methods

Create shipping extensions

Event System

Use events in payments