Last year a friend of mine & his wife went to the PI with their dog.
From what I recall they had to get an import permit from The Philippines Bureau of Animal. They also had a Health Certificate for the dog from a USDA vet.
They also had to get a specific flight that would handles transporting pets.

The import permit that they got for the dog was valid for 2 months - they were staying less than that.

Your best bet is to contact The Phillipines Bureau Of Animal Industries for info - they are the dept that handles import of pets and they would give you the most updated/correct info. Plus you have to go thru them anyway to get the import permit.