John would get [off the bus].
One party says that "get off" is a phrasal verb, so it should be [get off][the bus];
but another party says that "off the bus" should be a prepositional phrase, so it should be [get][off the bus].
We did some constituency tests (eg. "It was off the bus that John would get" and "John would get off the bus and on the boat.") but have different opinions towards the grammaticality of those sentences. The sad thing is that, since we aren't native speakers of English, our judgment seems not-so-reliable.
Can anyone (native English speakers especially) please help?
Thanks in advance. :)
EDIT: sorry for the typo, i meant to ask whether "off the bus" is a constituent...