If you have WHMCS installed and attempt to change the value of max_execution_time via the PHP INI Editor in either WHM or cPanel, you may find that any changes are apparently ignored even though the .user.ini and php.ini files are updated accordingly.

The reason for this is that WHMCS sets max_execution_time to 300 by default and this overrides the PHP INI Editor setting.

You can override this setting by adding the following variable to the configuration.php file in the folder in which you have WHMCS installed:

$overidephptimelimit=600;

The example above will set the max_execution_time to 600 though this value can be adjusted to suit your requirements.