In our experience (like 3 PHL trips, but it's been awhile...)
PA may or may not weigh things. Might depend on if they are using their own people in SFO or contracting it to a US carrier. Flying biz might help on the way there. Seems more likely to be an issue in PHL or upon return. Likely if it's a carry on that is of a (standard US carry-on) size that's probably overweight before you put anything in it. Better hope of passing if you have more of an "international" size carryon, which may be a requirement.
An individual PA agent may or may not care.
PA may let it go if you point out it's camera gear. They seem to let computers go - have had them look at a bag, ask if it has a laptop, and just let that go. I seem to recall reading some fine print in PA rules about computers, as if they get that they can be heavy or fragile and checking a laptop isn't really an acceptable option. Some agents may treat camera gear the same way. Or not.
Owner of a shop we travel with sometimes said he's seen someone in the line at PA take a heavy camera out of a bag, hang it around their neck or hand it to someone else, then they would let the bag go through (and of course the heavy camera would immediately go bank in lol.)
If you happen to be in a group with an "expediter" type local person helping with transit, that seems to help, but that would be mostly for checked luggage. Though we had a handy (US) group leader on our first PHL trip who chatted someone up on the plane and had us out of our seats before we were at the gate, and through some diplomatic line to make a tight connection, where I'm pretty sure nothing got weighed. I don't know if more than chatting was involved.
My husband has a DSLR with a big metal housing, strobes, trays, domes, arms, etc. He's always managed to get through there. He uses a camera backpack, which holds alot and weighs a ton, is a bit chunky when full, and uses it as his personal item which they _probably_ won't weigh. Keeps it on his back, acts like it's light, maybe helps that he's a big guy. Stashes some things in other bags however makes it work. Non fragile heavy things like arms are good things to check, also so they don't consider them potential weapons. Check what you can. (Also tools, as security anywhere seems to randomly be cranky about tools, no matter how small.) Acting like something is light and irrelevant anywhere may sometimes let you slide things by. I guess some people do the fishing vest thing.
Also, you'll get to save a little weight by checking your reg (if you were planning to carry it on) since that technically isn't allowed in the Philippines.
Note that low carry-on allowances aren't so much a Philippines Airlines thing, but common around the world on non-US carriers. So if you're going to travel other places with a big wad of camera gear, or on small planes, it's a thing you have to figure out. You develop different strategies for different places, And ideally you will have a plan B.
Before he got the backpack, my husband used to use a hard rollaboard Samsonite with pick and pluck foam. If they didn't let him on with it, it has a chance of survival if it gets checked or gate-checked. Only once did he have to check it, and that was in Australia. It arrived fine. (The bellhop in the hotel broke stuff instead, but that's another story.)
