I just spent a month in The Philippines. All you need is your passport and proof of vaccination. If you’re not vaccinated I am not sure what you need, but that is always changing. You can stay in Philippines for 30 days with no visa. Clark is a very new, nice airport. When going to Manila give yourself plenty of time, the traffic is terrible. It took my daughter 4 hours to go from near Angeles City to Manila airport. It’s around 60-70 miles.