From WikiPilipinas: The Hip 'n Free Philippine Encyclopedia
The Filipino alphabet (officially Makabagong alpabetong Filipino; English: Modern Filipino alphabet) is made up of 28 letters, which includes the entire 20-letter set of the Abakada, the alphabet of Tagalog, (including ng) and 8 letters from the Spanish alphabet (namely C, F, J, Ñ, Q, V, X and Z). It was once formerly known as the abakada when it was introduced by Lope K. Santos during the American colonial period as the alphabet for the Wikang Pambansa Batay sa Tagalog (English: Tagalog-Based National Language), as well as Tagalog. It is used today as the writing system for all autochthonous Austronesian languages in the Philippines and occasionally in writing Chabacano, a Spanish-derived creole.
 Adoption of the Roman alphabet
When the Philippine languages were first written in the Roman alphabet, they used Spanish orthography. This alphabet was called the abecedario. Relics of this can still be seen in the way "Castilianized" indigenous and Chinese-origin surnames are written, such as Macasáquit, Guanzón, Dimaculañgan, and others. Many indigenous place names are also written using Spanish orthography, often either coexisting or competing with their native forms if they exist (Bulacán/Bulakan, Caloocan/Kalookan, Taguig/Tagig, etc.). Parañaque would be written in the native system as Paranyake, but the latter spelling is so far unaccepted if at all heard of.
Abakada is the Tagalog alphabet, Tagalog having been selected as the basis of the national language in 1935, of 20 letters officially introduced by Lope K. Santos through his Balarila ng Wikang Pambansa (but initially employed by José Rizal who suggested replacing the use of both C and Q by simply K) during the American occupation of the country and adopted by the National Language Institute of the Philippines in 1973. The alphabet was called "abakada" for the letters were pronounced with the sound "a" at the end, for example b was pronounced "ba", l was pronounced "la", and so on. This alphabet of 20 letters has only one letter to represent each distinct sound in Tagalog—unlike, say, the letters 'c' and 'k' in English. The 20 letters of Abakada are written as a b k d e g h i l m n ng (where ng is considered as only one letter.) o p r s t u w y.
The National Language Institute initiated the new language in 1973. In 1976, the alphabet consisted of 31 letters—the 26 letters of the English alphabet, the Spanish ñ, ll, rr, and ch, and the ng of Tagalog. In practice, however, the digraphs are considered as their two constituent letters. In 1973 Pilipino was defined by law as the official language. The national alphabet was again expanded in 1976 to include the letters C, Ch, F, J, Ll, Ñ, Q, Rr, V, X, and Z in order to accommodate words of Spanish and English origin. The alphabet was then later reduced to 28 letters, rr, ll and ch, all of which are of Spanish origin, were removed, leaving 28 letters, in 1987 when Pilipino was renamed Filipino. (Ch, Rr, and Ll were themselves later abolished from the Spanish alphabet.) This current alphabet is basically the entire English alphabet plus the letters Ñ and Ng, alphabetized separately in theory.
 The Orthography of the National Language (Ang Ortograpiya ng Wikang Pambansa)
As of August 2007, the Commission on the Filipino Language has made available a draft version of Filipino orthography that is open for comment. This document is a result of a series of consultations with various teachers, instructors, linguists and others in the field that took place between 2006 and 2007.
The document begins by detailing the letters of the alphabet, their order and their names. One set of names is based on English letter names; the other, similar to the former Abakada. Some exceptional names are those letters which were not part of the Abakada: C, se, Q, kwa and X, eksa.
It goes on to name punctuation marks, and describes the use of the acute, grave and circumflex accents in Filipino. Words that already exist in the language are preferred over a borrowed term, for example, tuntunin vs. rul (derived from English rule). In terms of spelling, issues concerning the use of y-/iy- and w-/uw- are codified according to the number of preceding consonants and the origin of the word if it is borrowed.
Lastly, it provides spelling guidelines for words of foreign origin. It focuses mainly on the two languages that have provided a large number of lexical items to the Filipino language, namely Spanish and English. In short, regarding borrowings from these two languages, Spanish words of common usage are written in a manner consistent with Filipino phonology. These words are already in common usage, thus they will not revert to their Spanish spelling. On the other hand, if the words come from English or another foreign source or if the term is derived from Spanish that does not already have a phonetic spelling, the spelling should be kept intact; it should not be spelled phonetically.
Spanish teléfono = telepono NOT *telefono
English psychology = psychology NOT *saykoloji, but:
Spanish psicología = sikolohiya
 Order/Collation of the Alphabet
A B C D E F G H I J K L M N Ñ Ng O P Q R S T U V W X Y Z
 Samples of the Different Orthography Styles
Below is an example of the difference in orthography between the Spanish and Modern Filipino systems. The text used for comparison is the Filipino version of the Lord's Prayer.