I would agree with Camille, the roots look very healthy and the other leaves also look fine.
The potting medium and the pot looks odd. It looks to me like it is potted in polystrine balls which I think is unusual at least. I would get hold of some orchid bark or other orchid medium and pot it into a clear plant pot which should be just big enough to get the roots into.
You should water it when the roots turn silver rather than the bright green they are in the picture. If you use that as a guide to watering you should get the right balance of watering enough but not overwatering.
Usually Phals like indirect light, not sure about the specific one you have. At the momment I have mine in an east facing window so they get some direct light but only first thing in the morning.
I notice you are in the UK. I use the fertiliser in the link below which is a UK brand. If this is your only orchid you will find it will last forever as you will need about one drop each time you water. You should fertilise about once a week and then flush through with plain water once a month.
Chempak Orchid Growth Formula High Nitrogen Food 250ml