WHMCS

The WHMCS integration ships as two components that share a single API key:

a payment gateway (PawPayments (Crypto)) that pays any WHMCS invoice with crypto,
an optional addon (PawPayments Crypto Deposit) that adds an Add Funds page where customers credit their WHMCS balance with crypto.

Download the plugin (.zip)

Ready-to-upload pawpayments-whmcs-<version>.zip (gateway + addon).

View source on GitHub

Source, releases, and issue tracker.

Property	Value
GitHub	`pawpayments/whmcs-plugin`
Download	Latest release `.zip`
WHMCS	8.x
PHP	7.4+ (8.1+ recommended; WHMCS 8.x supports up to 8.3)
Required extensions	`curl`, `json`, `mbstring`, `openssl`
Database	Whatever WHMCS already uses (MySQL / MariaDB)

File layout

The release zip mirrors the WHMCS install tree:

modules/
├── gateways/
│   ├── pawpayments.php                          ← gateway entry point
│   ├── pawpayments/                             ← vendored SDK
│   │   └── vendor/pawpayments/sdk/...
│   └── callback/
│       ├── pawpayments.php                      ← checkout webhook
│       └── pawpayments_topup.php                ← top-up webhook
└── addons/
    └── pawpayments_topup/
        └── pawpayments_topup.php                ← top-up addon (Add Funds)

Drop those folders directly into your WHMCS root, then restore ownership:

chown -R www-data:www-data \
    modules/gateways/pawpayments.php \
    modules/gateways/pawpayments \
    modules/gateways/callback/pawpayments*.php \
    modules/addons/pawpayments_topup

Activate the gateway

Setup → Payments → Payment Gateways → All Payment Gateways.
Click PawPayments (Crypto) to activate.

Fill the fields:

Field	Value
Display Name	Customer‑facing label, e.g. PawPayments (Crypto).
API Key	Merchant API key from the Paw dashboard.
API Base URL	`https://api.pawpayments.com` (default).
Invoice TTL (seconds)	Lifetime of the underlying Paw invoice. Default `3600`. The same `payment_url` is reused inside that window.

Activate the Add Funds addon (optional)

Setup → Addon Modules → PawPayments Crypto Deposit → Activate.
Configure — leave the API Key field empty to inherit the gateway’s key, or enter a separate one.
Grant access to the desired admin roles, save.

The addon creates mod_pawpayments_credits on activation; this small table provides idempotency for the top‑up webhook (primary key on order_id). The customer top‑up page is then available at https://<your-whmcs>/index.php?m=pawpayments_topup. Link to it from a custom client‑area menu item.

Webhook URLs

The plugin sends notify_url on every invoice it creates, so manual webhook setup is not required. The endpoints are:

Purpose	URL
Checkout	`https://<your-whmcs>/modules/gateways/callback/pawpayments.php`
Top‑up	`https://<your-whmcs>/modules/gateways/callback/pawpayments_topup.php`

If the merchant account requires a default webhook URL, use the checkout one. Both endpoints must be reachable over HTTPS.

Lifecycle

Checkout. addInvoicePayment is called with the Paw order_id as transactionId, so duplicate webhook deliveries never double‑pay an invoice. Top‑up. Each top‑up creates a one‑shot Paw invoice via POST /api/v2/invoices and is recorded in mod_pawpayments_credits keyed by order_id. On webhook success the WHMCS AddCredit API is called, visible on Clients → Client Profile → Summary → Credit Balance. Webhooks carrying a permanent_address_id are silently acknowledged with 200 OK.

Smoke test (checkout)

ORDER_ID="<paw_order_id>"
INVOICE_ID="<whmcs_invoice_id>"
KEY="<your_api_key>"
BODY="{\"order_id\":\"$ORDER_ID\",\"extra\":\"$INVOICE_ID\",\"status\":\"success\",\"fiat_amount\":\"15\",\"asset\":\"USDT\"}"
SIG=$(printf '%s' "$BODY" | openssl dgst -sha256 -hmac "$KEY" | awk '{print $2}')

curl -X POST "https://<your-whmcs>/modules/gateways/callback/pawpayments.php" \
  -H "Content-Type: application/json" \
  -H "X-Paw-Signature: $SIG" \
  -d "$BODY"

Expected: OK with HTTP 200, and the WHMCS invoice transitions to Paid.

Troubleshooting

Symptom	Cause / Fix
Gateway not in the list at Setup → Payments → Payment Gateways	Files not uploaded or wrong path. Verify `modules/gateways/pawpayments.php` exists and is readable by the web user.
`Failed to create payment: Invalid API key`	API key wrong or merchant not activated.
Webhook returns HTTP 500 with `Failed to open required init.php`	Outdated callback. Current callback uses `require_once __DIR__ . '/../../../init.php';` (three `..`, not four). Re‑upload the latest `callback/pawpayments*.php`.
Webhook returns HTTP 401 Invalid signature	The API key in gateway settings does not match the one used to issue the invoice. Update settings and re‑issue.
Top‑up addon not visible	Activate it under Setup → Addon Modules and grant access to your admin role.
`Module Not Activated` on top‑up	The gateway must be enabled — the addon falls back to the gateway’s API key.
Duplicate top‑ups	`mod_pawpayments_credits` prevents this. If the table is missing, re‑activate the addon.

WHMCS gateway logs are at Utilities → Logs → Gateway Log (filter by pawpayments).

Uninstall

cd /path/to/whmcs
rm -rf modules/gateways/pawpayments.php \
       modules/gateways/pawpayments \
       modules/gateways/callback/pawpayments.php \
       modules/gateways/callback/pawpayments_topup.php \
       modules/addons/pawpayments_topup

Deactivate the addon and gateway from the WHMCS admin first. Optionally drop the bookkeeping table:

DROP TABLE IF EXISTS mod_pawpayments_credits;

Introduction

Migrate from another provider

Plugins & SDKs

Download the plugin (.zip)

View source on GitHub

File layout

Activate the gateway

Activate the Add Funds addon (optional)

Webhook URLs

Lifecycle

Smoke test (checkout)

Troubleshooting

Uninstall

Download the plugin (.zip)

View source on GitHub

​File layout

​Activate the gateway

​Activate the Add Funds addon (optional)

​Webhook URLs

​Lifecycle

​Smoke test (checkout)

​Troubleshooting

​Uninstall

File layout

Activate the gateway

Activate the Add Funds addon (optional)

Webhook URLs

Lifecycle

Smoke test (checkout)

Troubleshooting

Uninstall