how can my brother use my iphone 4s in the philippines?

Hi Bugaboo_45,

Thanks for posting your question about an iPhone 4s. I'm glad to see if I can help out.

Generally speaking, the best bet would be to make sure the phone is unlocked and then get in contact with the wireless carrier he wants to use in order to ensure it will be compatible with their network, and to activate service.

How to unlock your iPhone for use with a different carrier

Wireless carrier support and features for iPhone in Asia-Pacific

I hope this helps get you started. Take care.

Do this also: https://support.apple.com/en-us/HT201351