You phoned 4 years ago, the new rules was updated april 2007. Here is the complete guidelines ...
"New Rules on Dual Citizenship
PHILIPPINE IMMIGRATIONS: New rules on dual citizenship: Filipinos with dual citizenships can now enter end leave the country, trouble free, as long as they present both their Philippine and foreign passports to immigration officers at the time of arrival or departure, according to immigrations Commissioner Alipio Fernandez Jr.
This developed after bureau of immigration came out with new rules for arriving and departing passengers who availed themselves of the dual citizenship law passed by Congress last year.
Under the law, Filipinos who became, or are intending to become naturalized citizens of other countries, have not lost their Philippine citizenship. According to Mr. Fernandez, a Filipino who presents a foreign passport shall only be given an indefinite stay in the country if he or she can show a valid Philippine passport or a certificate from the BI as proof of dual citizenship.
The immigration officer then makes the appropriate stamp on both the foreign and Philippine passports of the passenger. Immigration executive director Roy Almoro said the new rules were issued in the wake of reports of misunderstanding between immigration officers and passengers with dual citizenship.
Airport immigration head of supervisors Ferdinand Sampol said dual citizens who entered the country using foreign passports will be cleared for departure provided they present a valid Philippine passport and bureau of immigration certificate.
The passenger is no longer required to present a certificate, exit permit or proof of payment of immigration fees. "
This was out to public 13 April 2007.