我可以在仍在运行时停止composer-php

Using composer-php, It's sometimes very slow and often I want to stop it.

If I stop it by using CTRL + C, would it be ok?

Would my script be half-updated or half-installed if I do this?

Yes, you can stop it. If you interrupted during a bad time, you should always be able to restore any composer-related files from your software versioning system.