This is an example plugin that demonstrates how to integrate license key validation for a content management system using the WHMCS Licensing Addon. It is intended for developers who sell premium plugins or themes and need a reliable method to verify customer licenses directly from their WHMCS billing and automation platform.

• WHMCS Integration: The plugin is configured to communicate with your WHMCS installation, sending license key data for validation and receiving a response to authorize or deny access.
• Local Key Caching: To reduce server load and maintain functionality during connectivity issues, the plugin can cache a local license key. You can configure the number of days between mandatory remote checks with the local_key_expire_days setting.
• Grace Period for Failures: A configurable allow_check_fail_days setting provides a buffer if the WHMCS server is temporarily unreachable, preventing immediate lockouts for legitimate users.
• Simple Configuration: Setup involves editing a single plugin.json file to input your WHMCS URL, product secret key, and the caching parameters, making initial integration straightforward.
• Developer Foundation: The code serves as a practical, open-source reference. Developers can study and adapt its structure and functions to implement secure licensing in their own commercial software projects.