These idiomatic expressions are not commonly used. Although they are sometimes used in some old types of stories or news on tv. You might want to remember them. tbh I myself didn't recognize these words at first sight. xD Anyways.. Aniko = Ani: said, ko: I (I said). We commonly say 'sabi ko'(sabi= say) Aniya = niya: she/he. Commonly said as 'sabi niya' Anila = nila: they. common as 'sabi nila' We also say Kako, Kaniya and Kanila only at the end of the sentence. Sometimes to make what we want to say shorter. They seem more casual than aniko, aniya and anila. I hope it makes sense.. ^_^

I'm not sure how often that particular expression is used because I never lived in a Tagalog-dominant area, but I can tell you that it's a contraction of "wika ni" (means the same thing as "sabi ni"). http://tagaloglang.com/Tagalog-English-Dictionary/English-Translation-of-Tagalog-Word/anila.html

Ani is not an idiomatic expression. Ani means harvest in Filipino. It is not a dialog tag and it does not mean "sabi ni" (said by). It is a corruption of the older "wika ni" or "wika niya" dialog tag and is not used on formal writings. Ani, ani niya, aniya, ika niya, are all informal, grammatically incorrect forms of "wika niya".