(First of all, a caveat. All of the commentaries I recommend in this piece are evangelical in their approach to what Scripture means.)
I want to start with an old classic from the late William Hendriksen, written originally in 1962. He is solidly Reformed in his exegesis and application. Hendriksen can be wordy and dry, but Philippians is one of his best commentaries.
For those with a good knowledge of Greek, I recommend Joseph Hellerman's recent volume in the Exegetical Guide to the Greek New Testament Series (Broadman & Holman, 2015). Hellerman does not go overboard with information, but provides a succinct explanation of clauses and words that is helpful for sermon preparation.
Moises Silva's volume in the Baker Exegetical Series (Baker, second ed. 2005) uses Greek as well, but he provides an English translation at the beginning of each section. Silva is concise, and does not often get lost in the exegetical weeds of the passage in question. He is always mindful of where Paul is leading us in the epistle.
Marcus Bockmuehl has written in the Black's New Testament Series (Hendrickson, 1998). This work is more moderate than any of the others I mention today. The book covers theology very well, and again makes good use of its space.
I need to put Gordon Fee (New International Commentary on the New Testament, Eerdmans, 1995) and G. Walter Hansen (Pillar New Testament Series, Eerdmans, 2009) together. Both are in similar evangelical-critical series, and both have a lot of pages in which to cover a 4 chapter letter. (Fee has 497pp, Hansen 351pp.) Greek is limited to footnotes. Both are readable and leave no stone unturned in their study of the letter. Both of these would be an excellent choice, but if limited to one such volume, pick Hansen which is much more recent.
Last, but certainly not least, is the Mentor Commentary volume from Matthew Harmon (Christian Focus, 2015). This volume combines exegesis and application in a way none of the others do. Each section closes with Suggestions for Preaching and Teaching. This series and volume is quite conservative, but it does combine the various aspects of exposition in a way few others do.
Other helpful works: John Calvin (1548), John Eadie (1858), Dennis Johnson (Reformed Expository Commentary, 2013), Tony Merida & Francis Chan (Christ-Centered Exposition Series, 2016)
