Check the requirements of your exact WHMCS release before installing it or changing PHP. A server that runs an older WHMCS version successfully may not support the next version with the same PHP and ionCube configuration.
IN THIS ARTICLE
01 Prepare a compatibility record
- Identify whether the installation is self-hosted or WHMCS Cloud. File, database and cron administration in this guide applies to self-hosted installations.
- Record the current and target WHMCS versions, web PHP, command-line PHP, ionCube Loader, database server and web server.
- Compare those values with the target release's versioned system requirements and release notes.
- List installed gateways, registrars, provisioning modules, addons and custom themes. Obtain compatibility confirmation for the versions you actually use.
- Check required extensions, database privileges, writable storage and the separate requirements of the automatic updater.
- Resolve conflicts in a controlled test environment before changing production.
02 Use current requirements carefully
WHMCS 9.0's published requirements support PHP 8.2 and 8.3 with the corresponding ionCube Loader. Do not treat a newer PHP version as automatically compatible. Its release also removes older PHP support and certain legacy Smarty tags, so a PHP change alone may not prepare an old custom theme.
Check the vendor's current support table when selecting a target release. Avoid a beta release for production solely because it has the highest version number.
Does WHMCS compatibility also establish addon compatibility?
Some addons impose narrower requirements than WHMCS itself. For example, the supplied Hosting Suite renewal accounting implementation is restricted to WHMCS 8. Resolve that billing dependency before approving a major-version upgrade.
03 Verification and next steps
Save the compatibility record with the planned installation or update. Define the tests that must pass, including sign-in, checkout, payment notification, provisioning, support email and scheduled automation.
If a requirement is unclear, ask the relevant software vendor or server administrator for the specific supported combination. Do not remove a required security or runtime setting just to silence an installation warning. Once the record is complete, follow the installation guide or the appropriate update procedure for that version.