If I have Chinese passport with a Canada/US visa, do I still apply to visit Philippines for 5 days?

Well, the authorities has implemented a new policy. Chinese passport holders enjoy 7 day free visit if they come to Philippines for tourist purpose. However, they should hold valid US, Japan, Australian, Canadian or Schengen visa. Meanwhile, their passports should be valid more than six months. They should also have return trips or onward air ticket. More importantly, they should not be banned by the immigration department.

So I think you needn't apply one in advance if you meet the requirements.