Make WHMCS support PHP >=8.0https://www.php.net/releases/8.0/en.php
WHMCS Team Clarification:
Ioncube Loader v12 is only compatible with PHP 8.1 and later environments. The previous Loader, v11, only supports up to PHP 7.4. This means that WHMCS will not run in PHP 8.0 environments. WHMCS v8.6.0 will operate in PHP 7.2, 7.3, 7.4, or 8.1 environments with the correct loader.
Version 8.6 has now reached public beta, which includes PHP 8.1 support: https://blog.whmcs.com/133721/whmcs-86-beta-now-available
Please join us during the pre-release testing period and provide your feedback in our dedicated beta community board: https://whmcs.community/forum/590-whmcs-86-beta-discussion/