Does transit in airport count as first country?

I have Belgian passport, and want to fly from Singapore to Xiamen, but my flight makes a stop in Manila (Philippines) and I have to change airplane to Xiamen, My thirth Country will be Philippines, Does the changing of airoplanes being seen as coming from Philippines or Singapore by the immigration in Xiamen, Probably I stay in the transit zone in Philippines but I am not sure.

Regards, Eddy