why is four seasons not occurring in the Philippines
The Philippines, like a lot of countries near the equator, especially islands, don't experience much temperature variations during the course of a year. This is mostly because the angle at which the sun's rays shine on the area does not vary much in terms of altitude in the sky. At farther northern and southern latitudes, the sun at midday can vary between near the zenith or close to the horizon over the seasonal cycle as opposed to equatorial latitudes where it is closer to the zenith (the point directly overhead) throughout the year. Seasonal variations are not as exaggerated near the equator.
Your country is at about 6 to 18 degrees north latitude so the sun stays fairly high at the midday times throughout the year, moving across the zenith into the north sky since it is in the tropics then back into the south sky throughout the year, but never going low enough to cause big seasonal changes.
I am trying to find an animation online to show what I mean, but can't find one right now. When I do, I will update the answer.
Here is the perfect animation
Click on "Sun's path in the sky (3 min 35 sec)"