# Advanced

## Introduction

The following are some advanced customisation options.

* **[Upgrading to WHMCS 8.0](/advanced/upgrade-to-whmcs-8/)**Everything you need to know to ensure a smooth transition to Version 8.
* **[Creating Pages](/advanced/creating-pages/)**Learn how to create additional pages within the WHMCS client area.
* **[Authentication via CurrentUser](/advanced/authentication/)**Learn how to assess the current authentication state with `CurrentUser`.
* **[Interacting with the Database](/advanced/db-interaction/)**Learn how to interact with the WHMCS database
* **[Date Functions](/advanced/date-functions/)**Learn how to use the date helper functions in WHMCS
* **[Currency Formatting](/advanced/currency-formatting/)**Learn how to use the currency formatting helper functions in WHMCS
* **[Logging](/advanced/logging/)**Learn how to use the logging helper functions in WHMCS
* **[Widgets](/advanced/widgets/)**Learn how to create widgets using AbstractWidget
* **[JSON File](/advanced/json-file/)**Provide meta information for modules
* **[OAuth](/oauth/introduction)**Learn how to set up OAuth with WHMCS.