You are aware that the permitted period of visa-free stay in The Philippines is 21 days? So for a month you will need either a visa before you go, or to apply for an extension once there, or to exit and re-enter.
http://www.gov.ph/faqs/visa.asp
My limited experience with Philippines bureaucracy suggests that the last option (maybe a couple of days in Hong Kong or Macau) might be the easiest, and maybe even the cheapest, option.

(Edit - oops - just seen in the other thread that you will be working, so I guess you'll be getting a visa anyway.)