I have 3 phal minatures, a Den a full size Phal and an Oncidium.
My full size Phal, which I believe to be a Woodlawn, has just lost its last flower, however there are two spikes, one appears to have a shoot coming out at the end, should I cut the other spike down now that the flowers have finished
About your Phal, if the plant looks strong and has a good root system, I generally leave the spikes on them as long as they are still green. They will rebloom. But if they are weak looking or has a poor root system then I would remove the spikes.
My personal preference is to cut spikes off as low as possible unless there is already a sign of a new side spike. In your case I would cut the spike which has nothing but leave the one with the side spike, possibly cutting it about an inch or two above where the side spike is coming from.
Whether or not to cut a still living spike is a matter of personal preference. Some people like to leave them until they turn brown, in case more flowers grow or even a keiki (baby) forms.