You file a full year resident PA return. When you move abroad, you are considered a resident of the last state you lived in until you change it.
References:
https://ttlc.intuit.com/community/state-taxes/discussion/re-do-expats-need-to-file-state-returns-if-...
https://ttlc.intuit.com/community/state-taxes/discussion/what-is-my-state-of-residence-if-i-don-t-li...
