This is what I just found at Philippine Embassy Washington DC website:
6. WHAT ARE THE IMPLICATIONS ON PAYMENT OF INCOME TAXES?
Under the Philippine Comprehensive Tax Reform Program of 1997, incomes earned overseas by Filipinos from 1998 onwards are no longer taxable by the Philippine government. Hence, all Filipinos abroad, including those who have retained/reacquired their Philippine citizenship, have been exempted by the Philippine Government from paying Philippine income tax on incomes earned abroad.
Incomes earned in the Philippines, however, will be subject to Philippine income tax.
Prospective applicants are advised to visit and read the contents of the website of the U.S. Internal Revenue Service, which contains information about current U.S. government policy on taxes on incomes earned worldwide, or to seek legal advice from a U.S. tax lawyer.