So I've been doing some research on this topic, cause it may soon impact me, and I have heard different things. The first is that contract and temp jobs don't really count in the whole quitting before a year and second that even in jobs that do a lot of places say you get one freebie, then there are a bunch of negative opinions towards it. I know a lot of people who have left jobs in under three months when they got a position they really want and have just neglected to put the job they left on their resume. You'd just have to weigh the trade-off of being able to claim those eight or so months of experience against the fact that you might get a bad reference from your first boss. Crazy thought is your job close to any school you applied to, so that there's some way you can semi-finish the year out while actually in school, like on the weekends or something.
Personally, I think the best move is to either defer if you don't have to go to PhD right now; or explain the situation probably completely honestly and hope your boss understands. Though you could always say something like you had no intentions to apply when you first got the job but you were sent a fee waiver from the school and decided to apply on a whim and ended up actually being accepted and have now decided to go. I know last year Notre Dame sent me a fee waiver to their grad school last minute so I just decided to say why not and send off an application so there is precedence. Honesty is probably the best policy though because once you start lying the whole thing can just blow up in your face.