I didn't know it made a difference in the Philippines. What I do is scratch the back off with a coin to get the code. Go on App Store. Scroll all the way to the bottom and click redeem. Enter the code.
Go to your App Store, click the button that says redeem, type in code and your money from the card automatically gets added to App Store, and iTunes. You can either purchase music, or games, exec.
I didnt know the Philippines had itunes card, didnt see one when i went back there lol. Try connecting it on your computer and see if you can redeem it straight from itunes.. if you dont have itunes on phone like how anya said. Or just go to the website o.o