According to Google, Davao, Philippines sits at about 7 degrees north of the equator, which isn't very far from the equator at all. The equator gets a lot of sun year-round since the Earth is tilted. If this doesn't make sense to you, grab a little styrofoam ball and draw a circle around its middle. Tilt the ball, and take it on a circular route around a light bulb or some other stationary object. Look at how the light hits the ball. It will be more shadowy at the "pole" that is facing farther away from the light source. Davao still has "winter" -- just not the very cold weather typically associated with it!

Davao is tropical; it is located near the equator.

Winter is caused by the tilt of the Earth's axis that tilts one hemisphere away from the sun, and then the other hemisphere. The tropics are always in the full light of the sun, though, so they do not have seasons the way that places farther from the equator do.