Cheapest way to send a lot of my stuff from Vancouver to Philippines

What's the cheapest way to send three to six two-cubic-feet corrugated boxes of stuff from Vancouver to Manila?
For this cheapest way, would I be charged by volume or by weight? Because if by volume, I may want to include heavy stuff, such as stuff from my pantry (canned foods, bottles of ketchup, spices, olive oil, etc)

I don't mind if it takes several months. Most important consideration is price.