My volume on my iPhone 4 stopped working the next morning what shall i do?

The other night my iPhone 4 volume worked and the next morning it just stopped working

Well, if you haven't already, reboot it. If that doesn't help, what i did when my volume switches died - I lived with it by going to "music", and using the volume control on the screen.
It doesn't "fix it" but it makes the volume useable again.