Cent OS 8.
I got an error while configuring icingaweb2 (stage command transport setup)
To fix the error you need to install php-json:
#dnf install php-json
Please, add this command to docs.
Again your chance to submit a pullrequest 
Hello there,
did you submit an issue on github?
It’s easier for us if we have all issues collected there
A pull request would obviously also be greatly appreciated 
Have a nice day!
Feu