Johnny Air Cargo. Ship it to their US warehouse (Delaware or NYC) and they'll forward it to the Philippines. You can pick it up at their Makati branch. I use them myself. Way better than trusting a stranger with an iPhone.

I did this a few years ago from Georgia to Davao, and my cousin ended up paying customs.

If it's a new iPhone, you're better off just buying it in the Philippines. Plenty of shops at Greenhills mall in the Manila area have the new iPhone 18 Pros, and you can get a good price since they're grey market. Even with the markup here, it'll be cheaper and faster than buying it in the States, paying a hundred dollars or more to ship it, and then dealing with customs charging several hundred on top of that.

I tried USPS and they sent it back to me before it even left the country because of the battery. I ended up just bringing it when I went to visit.

I reached out to my Marine groups in the Philippines. They found a guy who had my new ATM card mailed to his house, and he brought it over. Marines trust each other with that kind of thing.

Just a heads-up: a used phone might have prohibited content on it. There's really no way to tell whether a phone in a box hasn't been tampered with. I don't know the OP, this is just a general word of caution.