Why is he giving mixed signals?

About 4 months ago, my guy friend friendzoned me and said that he doesn't think that he will ever see me as more than a friend.Then a month later, he asked me if my bff if she told me anything about a guy I liked, (because she asked him about him when I told her not to).Then 2 months after that, he came to my birthday dinner, teasing and joking around with me including flirting with me a bit by sliding towards me, joking about "we're going out", and trying to pay for the people to come sing at my table. We barely talk, but he texted me out of the blue and invited me to his party. Im over him now, but why the mixed signals?