PPL in Phil.
I don't know if it's the cheapest but I guess by international it is cheap. You can try Omni Aviation based in Clark Field, Pampangga.
There are a lot of flying schools based in Manila, but your friend would probably waste too much time getting bogged on ground waiting for taxi clearance. NAIA (Manila) is such a big mess!
If your friend wants to be based in Manila then I guess the best choice would be Airlink Aviation.
Don't know about current rates but I check it out for you.
Later