Why is the Philippines considered a state?

The Philippines is a sovereign nation. One meaning of the Word "state" is "sovereign nation." In that sense, the Philippines is a state.

The other meaning of the Word "state" is as a semi-selfgoverning element of a sovereign nation that is organized as a federation. This is the meaning of the Word used when speaking of the State of California in the US or the state of Michoacán in Mexico. The Philippines is NOT a state in that sense.