Remember: sine waves can be calculated using two axes (x and y) but what happens if we add a third axis of depth (z)? It would be interesting if in 3D form it looked more like a spiral than a wave.
Same with phi. We always look at it three-dimensionally, but what if we added depth...would it not be spiral-shaped, much like I'm supposing a sine wave is?
Remember: out of an infinite possible viewpoints, from only one will a three-dimensional object apear two-dimensional, and a two-dimensional object one-dimensional. We humans have that uniqueness in our perspectives.