At the end of the first map, Luke and Cory call out "NEW MAP!" Luke then stops and prompts Nat to join in, showing how he's already accepted the newbie as part of the group.
Luke asking Nat if she wants to see a movie with him after the Buggy Arc.
After teasing Phil a little, Luke comes up with the idea of Luffy knowing his father to make his entry into the group a little smoother. He also keeps commenting that Phil's fitting in just fine, welcoming him to the group despite how Phil's implictedly mocked their hobbies in the past.
GM lies about Phil's roll, letting him defeat Jango. It's a huge Pet the Dog moment and it probably factored in...
Phil's decision to join the group. He was making fun of them only hours before and by the end of the night he's happily joined the group. There isn't a big moment where he says it was a lot of fun or that he was wrong for being a jerk. He just joins without a second thought.