Allow user to attach callback in Symfony process that gets fired when status changes

[nicholasnet]

Q	A
Bug report?	no
Feature request?	yes
BC Break report?	no
RFC?	yes
Symfony version	3.3

Currently Symfony process allows user to attach callbacks to listen for output but it does not allow user to attach callback that gets fired during status change like completion, success, abort, error etc for async one. Right now only way to monitor the status is to check constantly in a loop which is bit inconvenient in my opinion.

[sstok]

This is only possible when you monitor the activity as PHP as no native promise/async functionality. So unless this comes available (yes there are libraries, but these are still very young) it's not really possible at the moment.

[fabpot]

Closing as that's not something we can easily support in Symfony.