Originally Posted by Asian Spirit
Sounds like you might be using Philippines Airlines. Either way, in most cases where you have a layover of two hours or under you will be deplaned into and remain in a secure area and will not clear immigration or customs in Manila. To be sure it is best to call the airline(s) that you will be using to be sure.
Every other country I have flown into then gone on to my final destination, you will clear customs and immigration at first point of arrival, in this case Manila. (Flown into US, Canada, PNG and the EU then gone on to final destination.) Flying into the US then on to a foreign destination from Canada you have to clear US customs and immigration in Canada.
You often have to change terminals or at least transit from international to domestic sections of the terminal.
Only exception I know if is the PAL flight Manila to Vancouver then on to Toronto. There they deplane and re board in Vancouver but clear customs in Toronto. You cannot get on in Vancouver to fly to Toronto on that flight.
Call the airline and check to be sure.