Version 5.x System Requirements
From WHMCS Documentation
Most current web servers with PHP & MySQL installed will be capable of running WHMCS. However, the specific system requirements are:
- PHP Version 4.2.x or later except 5.3 (see below)
- MySQL Version 4.1.x or later
- Curl Support (with SSL)
- GD Image Library
- Ioncube Loaders
N.B. We've been finding that WHMCS will not function with on PHP 5.3 at the moment due to incompatibilities with Ioncube and PHP 5.3. You will need to downgrade to PHP 5.2.x until Ioncube releases updated loaders for it.
If you would like any more information or need help in determining if your server meets these requirements, please contact us.