I just bought a hydrangea and I am planning to transplant it to a pot, could we even grow hydrangea in pots?
Yes, just provide it its normal requirements. Give it some morning sun, afternoon shade or put it in bright shade. You will have to water it and fertilize it more often since it is in a pot. You can start with a pot size of around 18" or so.
One catch is to keep the size at maturity in mind. You do not want to plant a large hydrangea in a pot. In case the shrub gets large, for example. Repot to a larger size when you see that the roots are circling (check once a year or once every two years). When repotting, use a new pot that is about 2" larger than the previous one. Feel free to move the pot around if necessary during the year. Protect it from really bad inclement weather by storing it in a garage temporarily. Remember to continue watering when it goes dormant.
Regularly amend the potting soil to prevent iron chlorosis (or if you are trying to change the bloom color)and do not place the pot in a windy location. I like to put rocks at the bottom 1" of pots.
Will the Philippines be too hot for keeping hydrangeas as a perennial shrub? Won't it need some cold period to set buds?
Not at all. You can grow them and there is even one fragrant lacecap that originated from the area around the Philippines and Japan!
Actually, there tends to be a huge range of climates in Asia - Japan is very temperate (like much of the west coast; z7&8) while much of the Philippines is tropical/subtropical (like Hawaii; Z11&12). Most hydrangea species will not grow well or survive long in a tropical environment - they are for the most part temperate plants and require a period of cold for proper dormancy.
Hydrangeas (as westerners know them - macrophyllas, serratas, etc.) can be grown in the Philippines in cooler areas or under more controlled, greenhouse conditions. Would doubt their performance under open garden conditions.......