filter / philter are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
filter: (noun) device that removes something from whatever passes through it. (noun) an electrical device that alters the frequency spectrum of signals passing through it. (verb) remove by passing through a filter.
philter: (noun) a drink credited with magical power; can make the one who takes it love the one who gave it.
filter: f·IH·l·t·er
philter: NA
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)