Mabuhay! Depends where in the Phils you're going. You can't take knives on ferries and flights, but I managed to take an Emerson Combat Karambit and a Ka-Bar TDI on the ferry from Cebu City to Bohol. You can carry a knife into a mall if it's in your pocket--they only check your waist and bag. If you get stopped by the police, they might ask you for a bribe since it'll be considered a "deadly weapon". Certain cities in the Phils are more lenient than others.
Being Pinoy-American, you might get away with less than I do (since I'm foreign). I've been there three times this year, and I'm going to Manila again in July.