You MUST have a return or ONWARD ticket to legally enter the Philippines as a non-resident/citizen.
It has been that way for at least 20 years.
Recently (during the past week) they've been clamping down and actually CHECKING...though normally they didn't.
Your outgoing airline staff will normally check anyway though, as they are the ones who will be fined a lot of money for permitting you to fly without conforming with entry requirements.
