For your fellowship (epi tēi Koinéōniāi humōn). “On the basis of your contribution” as in 2Co 8:4; 2Co 9:13; Act 2:42. The particular kind of “partnership” or “fellowship” involved is the contribution made by the Philippians for the spread of the gospel (Phi 1:7 sugKoinéōnous and Phi 4:14 where sugKoinéōnēsantes occurs).
In furtherance of the gospel (eis to euaggelion). “For the gospel.”
From the first day until now (apo tēs prōtēs hēmeras achri tou nun). As when in Thessalonica (Phi 4:15.), in Corinth (Act 18:5; 2Co 11:7-10), and now in Rome.