no it doesnt work

This is not really a kata issue, since it's considered cheating.

"parsing" each command evey time is not efficient, and the test code do this a lot when jumping between lines.

This is great!

Good to know.

I also made a real solution for this kata beforehand, for what it's worth.

noted.

Thanks for reporting it, but use spoiler flag next time.

Thanks for showing me the '??' - operator. Wasn't aware of it...

use intdiv() for divisions and it should work.
the division in that sequence should result in 0, not -1

No spoilers but; that error is directed towards the line it's on. Re-read the instructions, because there's a case you're missing.

took me a lot of time rethinking my approach but I finally managed to write a working solution.
Good kata!