That is, added to plastics (especially PVC) to make them more flexible. It's of some controversy because of health effects, especially on prenatal development; Wikipedia has a brief summary and oodles of further reading. Phthalic acid, fwiw, is a aromatic organic dicarboxylic acids, C6H4(COOH)2, which is synthesized from naphthalene, from whence its name, it being an aromatic aromatic bicyclic hydrocarbon, C10H8, used in mothballs (so now you know how it smells), which in turn is named from Greek naphthas, used for any sort of petroleum or pitch, especially coal tar, in turn borrowed from Persian, from a root meaning to be damp. (The first half of napalm comes from naphtha.) Cycling back, so to speak, to the word itself, if it helps you pronounce it, treat the ph as silent.
After an hour of this, I concluded she blamed the decline of all civilization to high fructose corn syrup, phthalates, and kids these days.