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I'm afraid, I won't be able to help you with this particular issue due to time constraints.
But if you're interested, you can help by testing and reporting bugs on the new version that I'm working on, to update Apcal for PHP 7:
https://github.com/mambax7/apcal
This is ONLY for testing, and there will be bugs, but it would help to speed up the conversion by pointing them out.
Besides PHP 7 compatibility, Apcal would get namespaces and class autoloading.