Passing variables using the php -q method (php cli) requires the php directive register_argc_argv set to On (or 1) in the php.ini file. The same is necessary if you want to use option flags from WHMCS with the daily cron.
If you have a vps or dedicated server, then this should not be a problem. If you use a shared hosting account, then I would recommend to contact your hosting provider. Some providers, like ResellerClub, allows the use of a custom php.ini while others do not offer any solution or workaround.
An other solution to get this working would be using the GET method instead of php -q for the cronjob.
2018! A new challenge with a lot of changes coming up ...
We just released for all v3 and v4 Modules updates to be in compliance with the new upcoming WHMCS 7.5 system requirements for PHP 7.1. All modules have been reviewed and updated where necessary to work with PHP 7.1 and also to address some bugfixes.