Has anyone ever used pvc for the supports under a wood deck walkway? I have been told you can use it and it saves having to use concrete and dig holes but cannot find any information on it.

I suppose its possible to design a post made of PVC... but it would have to be specifically built as a supporting post. The manufacturers would list the weight it could support etc. However, I've never heard of this and can't imagine doing it. PVC is brittle in cold weather and too flexible in warm.

Everything lasting that you build needs a foundation. Not having proper foundations & not using something with appropriate structural rigidity is a recipe for trouble.

I too have not heard of this and would suggest preformed concrete pads designed to accept a 4x4 to support the deck. Even with this you need to dig through the soft black dirt to reach stabile soil, like clay or rock. You could also dig a hole passed your frost line and set a 4x4 or 6x6 pressue treated lumber in the hole with pea gravel back fill.