1987 Constitution of the Philippines
Section 7. The President-elect and the Vice President-elect shall assume office at the beginning of their terms.
If the President-elect fails to qualify, the Vice President-elect shall act as President until the President-elect shall have qualified.
If a President shall not have been chosen, the Vice President-elect shall act as President until a President shall have been chosen and qualified.
If at the beginning of the term of the President, the President-elect shall have died or shall have become permanently disabled, the Vice President-elect shall become President.
Where no President and Vice-President shall have been chosen or shall have qualified, or where both shall have died or become permanently disabled, the President of the Senate or, in case of his inability, the Speaker of the House of Representatives, shall act as President until a President or a Vice-President shall have been chosen and qualified.
The Congress shall, by law, provide for the manner in which one who is to act as President shall be selected until a President or a Vice-President shall have qualified, in case of death, permanent disability, or inability of the officials mentioned in the next preceding paragraph.