Small programs that actually run.

Each one is a few files you can download, point at your sandbox keys and watch take a payment. They are deliberately short, so the payment path is the only thing on screen. Read the developer guide for the reasoning behind them.

Server

A checkout in Node.js

One Express file that takes a payment end to end: it prices the order, creates a checkout, sends the customer to it, and marks the order paid when the signed webhook arrives.

Requires: Node.js 22 and a tunnel, so the webhook can reach your machine
SHA-256: 2701dd676211c18c06b6d0c998252d2770d1d2e8d0d1d58a2f3cabce5999be5c

Download39 kB

Run it

unzip payments-lk-sample-node-express-checkout-0.2.3.zip
cd payments-lk-sample-node-express-checkout
npm install             # the Node.js SDK comes from npm
cp .env.example .env    # then put your sandbox keys in
npm start

What it shows

Pricing the order on the server, never from the browser
An idempotency key per order, so a double click makes one checkout
Verifying the raw bytes with express.raw, because the signature covers what we sent
Fulfilling from the webhook and treating the return as a way back for the browser

Server

The same, in PHP

Two files. One prices the order and redirects, the other verifies the signed event and records the payment. No framework, so the payment path is the only thing on screen.

Requires: PHP 8.1 with curl, and Composer, which installs the PHP SDK from Packagist
SHA-256: b267be1aed86b11f3576508689e5bbcf6ce1233fb404561523ecfa21425fff09

Download8 kB

Run it

unzip payments-lk-sample-php-checkout-0.2.3.zip
cd payments-lk-sample-php-checkout
composer install        # the PHP SDK comes from Packagist

PAYMENTS_LK_SECRET_KEY=sk_test_... PAYMENTS_LK_WEBHOOK_SECRET=whsec_... php -S localhost:4242

What it shows

Reading php://input before any decoding, because a rebuilt body never verifies
An event handler that is safe to run twice, since a delivery can arrive twice
A thank you page that shows what the webhook recorded and decides nothing

Agent

An MCP agent

Calling the MCP server from your own code: list the tools your key allows, summarise a day, find a payment, then prepare a refund and wait for a person to approve it.

Requires: Node.js 22 and an agent key from the dashboard
SHA-256: 90d5b99bf8f6d92ce124ee9e204be198597425a2594aa715f37360b1893959c0

Download6 kB

Run it

unzip payments-lk-sample-mcp-agent-0.2.3.zip
cd payments-lk-sample-mcp-agent
npm install
PAYMENTS_LK_AGENT_KEY=ak_test_... node agent.mjs

# and to watch the approval path
PAYMENTS_LK_AGENT_KEY=ak_test_... node agent.mjs --refund pay_... --amount 100000

What it shows

The key as a bearer token in a header, never in the URL
Scopes deciding which tools exist, so a missing tool means a missing scope
A refund that is prepared, then approved by a person, then read back with get_action

Running a shop already?

On WooCommerce, PrestaShop or OpenCart there is nothing to write. Install the plugin for WooCommerce, PrestaShop or OpenCart, paste a key, add a webhook and take a test order. For anything else the SDKs cover Node.js, PHP, React Native, iOS, Android, Flutter and a pay button for any web page.

Check what you downloaded

Compare the SHA-256 beside each sample before you run it. Every archive is built from the Payments.lk repository, unzips into one folder named for the sample, and holds nothing but that sample’s files.

shasum -a 256 payments-lk-sample-mcp-agent-0.2.3.zip