There is little promoted Air Passenger Bill of Rights in the Philippines. Unsurprisingly, it is hidden in the legal notices on the PR website (6th paragraph from the top):
https://www.philippineairlines.com/a.../legal-notices

When the Covid Pandemic started I was in Manila and my PR flight to HK was suddenly cancelled due to government restrictions. PR re-booked me on CX without too much arguing. As always, it is best to know your rights, be firm and polite.