WHMCS API Integration: Best Practices and Examples

WHMCS API Overview

The WHMCS API allows external applications to interact with your billing system.

Authentication Methods

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API Credentials

The most common method using identifier and secret.

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Admin Authentication

For trusted internal applications.

Common API Calls

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Get Clients List

$results = localAPI('GetClients', ['limitstart' => 0, 'limitnum' => 25]);

#

Create New Order

$results = localAPI('AddOrder', [
    'clientid' => 1,
    'paymentmethod' => 'paypal',
    'pid' => [1],
    'domain' => ['example.com']
]);

Rate Limiting

Implement rate limiting to avoid overwhelming the API.

Error Handling

Always check the result field in API responses.