Some place long ago I read something that attempted to link the Philistines to the Phoenicians. It would be interesting to compare the DNA.
I don’t think they were (at least initially) Phoenicians. The Phoenicians called themselves Canaanites and had moved from the Persian gulf around 2000 BC. The Philistines had a non-Semitic base, but what that base was is open for debate. They most definitely got assimilated with the local Semites (Judeans or Canaanites).
also, the Philistines seem to have had Indo-European names — Philistine name Goliath (compare Lydian Alyattes, Greek Kalliades) (from Wikipedia) — which makes kind of sense. Perhaps the Dorian Greeks pushed the Ionians to go south?