With the popularity of orchids found in about every garden center today, this question is becoming more common.
This question is also being asked of Denbrobium and Cattleyas. Cattleyas are even being grown under artificial fluorescent lighting.
Most of the time you can easily cut the flower spike with a clean, sharp tool. I’ve always used box cutters with a razor blade I can change out.
Phalaenopsis orchid care sometimes is a process of trying to force the plant to rebloom for the old flower spikes. Other orchids you should remove the spikes right away after the last bloom has made its final curtain call.
You can encourage your orchid to rebloom again by cutting the flower spike right before the scar left from the first flower. If your orchid does rebloom, keep in mind it does take energy from the plant. If your plant is not healthy and thriving do not try to rebloom the plant.