Khalfaka versus Fī d-Dāri

Al-Mafʿūl Fīhi: Adverbials of Time and Place

Jalastu khalfaka: khalf(a) is a directly accusative place adverbial, with attached genitive pronoun.
Jalastu fī d-dāri: fī governs the genitive noun dāri.

Both describe locations, but the surface constructions differ.