People are asking when the Philippine National Language was established. (Kailan itinatag ang pambansang wika?)
On July 14, 1936, the National Language Institute designated Tagalog as the basis of the Philippine National Language.
According to Wikipedia.org, the national language became known as Pilipino in 1959.
Later on, the 1973 Constitution replaced Pilipino with Filipino.
In another Wikipedia entry, the “1987 constitution designated Filipino as the national language, mandating that as it evolves, it shall be further developed and enriched on the basis of existing Philippine and other languages.”
If you check the UP Filipino Dictionary, you’ll find some words marked as Bicolano and other languages in the Philippines. In other words, Filipino is not just Tagalog.
In actual practice, however, you’ll hear mostly Tagalog words when people converse in Filipino.
Anyway, you may wish to read The Metamorphosis of Filipino as National Language by Jessie Grace U. Rubrico:
But after more than 60 years, has Filipino truly metamorphosed into a Philippine national language? To what extent? What has been its “success stories”? Its failures? What is its current state or condition in the present? What needs to be further done? What is in store for the future? What are the development prospects of the other non-Tagalog languages of the Philippines for integration into Filipino? What are the pervasive influence of English or of other foreign languages on today’s speakers?
We hope this helps you in your research.