The hang that you experience is documented and expected behaviour.
PHP will hang until the application execution ends. This is why I suggest you the code above, the documentation mention you can avoid the hang if you redirect the program output Not to the "screen".
Also notice currently I avoid the use of the BAT file - it’s unnecessary to make such a complication while you can make it simple, and while you can do all and more just with php.
Also make sure the application (ProjectNissan.exe) exit after finishing the task as soon as possible. Don’t let the program work for ever.
Also consider what already said above, it can be a Permission issue - Windows do have some sort of file and execution permission. Some time its basics and some time it’s more advanced.
So for testing grant all the possible permissions including the advanced once
I wish I could help you more, but currently I don't have the tool and resource to make the necessary test and checking.
I can't even tell if the code I write above will 100% work/correct.
But give it a try - good lock
Microbz