The first thing not mentioned is why thereis a Catholic country in South East Asia at all (hint:colonialism). The second question is, what does this have to do with ISIS, half a world away (hint:nothing). The third question is what the frak is the president's responce going to result in? (Hint:lots of dead people).
So in order, The Phillipines was a Spainish colony, hence the Catholicism, that leaves Islam as a minority in the country and seems to have left some Muslims disgruntled at the situation.
It then became a colony of the US after they decided Spain didn't need all these colonies. And since they didn't copy Iran, i suspect that makes then a current US client state.
2) ISIS brand terrorism seems to he doing a fantastic job, it makes some media outlets sell good money, and on the ground groups have a rallying cry and flag to follow. But that's about the lenght of it. 'Fighting ISIS' in the Phillipines will have no material impact on the existance of the Islamic State in the middle east, other than using the same flag they share next to nothing, and i've heard reports that ISIS denies any affiliation - so it looks like this is a cheap knock-off brand...
3) Martial law in the Phillipines means the army are being used to arrest people and search for weapons. Armies doing police work tend to do it orettybadly, and the attitude of the president Duterte seems to be that killing them all is fine. This is libable to backfire worse than the UK sending the army in to do policing in Northern Ireland, (and at least there the orders were to do peacekeeping, not to shoot people).
Overall this smells like colonialism, and any news story you see which doesn't mention the history of bloodshed and politics is not really understanding the root of issues there. (Unfortunately i don't have a enough background in the details yet, but there are clearly places to research if you feel so inclined).