i reread it a few times, Phil definitely became a vampire..! The way Ed said "Why is he acting like a human?" or the way Phil kept asking Alice "Do I look strange?". Also Ed's apparent regret of taking away Phil's future. Lots of hints. But the biggest one is that when Phil said that as a human it is only natural to grow old and die but eventually said he's glad he choose Ed.
Sute Neko no Ie