poison = /ˈpɔɪz(ə)n/ If you count the individual phonemes, this makes six. The first syllable has a diphthong made up of the two phonemes ɔ + ɪ, so you could consider this to be one 'sound' if you like. This transcription (taken from the Macmillan dictionary) suggests that the schwa /ə/ in the second syllable is sometimes dropped, but I would still count it. squirrel = /ˈskwɪrəl/ This is seven phonemes and two syllables in BrE. I hope that helps.

I wonder what "phoneme" means in your question. If it means almost the same as "syllable", I'd say that both of then have two.