my iphone 5s camera is displaying nothing but black

Try a Forced Restart.

Force restart iPhone - Apple Support

You could test if it’s just the one camera, ie the front or back, or both!

You could also try a free third party camera app to see if same happens.

Failing any of the above try Restoring the device preferably via iTunes and setup as “New”.

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

If you don’t have access to a computer you can use “Erase” from the devices settings instead (see above link).

If nothing seems to work then book a Genius appointment to get hardware tested.

Zahmed23 wrote:

No it didn’t work

If by that you mean force restarting, using another camera app and restoring as new all failed then it may point to a hardware issue because you have basically eliminated all the software possibilities (that's my take on it anyway).

The only thing left is to see a Genius and get said hardware tested, can't think of anything else a user can do.