Work visa required?

I am a computer programmer working from home. I am based in the US, with the company headquarters just outside of Washington DC. My children are going to school in the Philippines, and my wife is there to take care of them. My question is this: If I go to the Philippines and stay for two or three months twice a year, do I need a work visa (or any other special documents) while I am there?

It is my understanding and I don't know if this would hold up in court or not but, if your income is derived from outside of the PH and you are not taking a job away from a local Filipino that you can do your overseas job while here. Look at all of the bloggers making money here from articles that they write while here. Again, who knows how things would go if someone here got a case of attitude with you over something, has friends in high places and reported you. I would just stay low key about it and keep your business to yourself while you are here.
Here is an article that I read a little while ago though.

http://philippineslifestyle.com/work-pe … er-regime/