Will I be able to use my Iphone 4s bought in Japan in Philippines

You will have to contact the wireless carrier in Japan to which

the iPhone is locked and see if they offer unlocking and if you

qualify. The last I knew, Japanese wireless carriers do not offer

unlocking; my advice is to sell the iPhone in Japan and buy

one locally in the Philippines. If I am wrong about Japanese

carriers unlocking, someone will surely jump in and let us know.

imobl is correct; the Japanese carriers do not provide unlocking services. So you will not be able to use any Japanese iPhone with any other carriers, and you should indeed sell it and buy one in the Philippines.

Regards.