Amendments to the Constitution can be proposed by one of three methods:
All proposed amendments, regardless of the method of proposal, must be ratified by a majority vote in a national referendum.
There have been five constitutional conventions in Philippine history:
None of the proposed amendments to the 1987 Constitution has succeeded, because none have reached the ratification by referendum stage.
The Official Gazette website on the Philippines Government web portal (open access) contains all Constitutions (as enacted and as amended), from the 1899 Malolos Constitution to the current 1987 Constitution.
The LAWPHiL Project website (open access) contains the 1899 Malolos, 1935, 1972 and 1987 Constitutions.
A new draft Constitution was prepared by the Philippines Constitution Consultative Committee and submitted to President Rodrigo Duterte on July 9, 2018. See the draft on CONSTITUTIONNET together with up to the minute news on the progress of the proposed Constitutional reforms.