Paul's authorship of Philippians is "universally accepted" (Beare, p. 1) by virtually all Bible scholars, ancient and modern, with the exception of the kenosis passage in Philippians 2:5-11. According to some theologians this may have been a Christian hymn that Paul quoted.
The letter was written to the church at Philippi, one of the earliest churches to be founded in Europe. They were very attached to Paul, just as he was very fond of them. Of all the churches, their contributions (which Paul gratefully acknowledges) are among the only he accepts. (Acts 20:33-35; 2 Cor. 11:7-12; 2 Thess. 3:8). The generosity of the Philippians comes out very conspicuously (Phil. 4:15). "This was a characteristic of the Macedonian missions, as 2 Cor. 8 and 9 amply and beautifully prove. It is remarkable that the Macedonian converts were, as a class, very poor (2 Cor. 8:2), though the very first converts were of all classes (Acts 16); and the parallel facts, their poverty and their open-handed support of the great missionary and his work, are deeply harmonious. At the present day the missionary liberality of poor Christians is, in proportion, really greater than that of the rich" (Moule).
The Philippians had sent Epaphroditus, their messenger, with contributions to meet the needs of Paul; and on his return Paul sent this letter with him. With this precious communication Epaphroditus sets out on his homeward journey. "The joy caused by his return, and the effect of this wonderful letter when first read in the church of Philippi, are hidden from us. And we may almost say that with this letter the church itself passes from our view. To-day, in silent meadows, quiet cattle browse among the ruins which mark the site of what was once the flourishing Roman colony of Philippi, the home of the most attractive church of the apostolic age. But the name and fame and spiritual influence of that church will never pass. To myriads of men and women in every age and nation the letter written in while he was under house arrest in Rome, and carried along the Egnatian Way by an obscure Christian messenger, has been a light divine and a cheerful guide along the most rugged paths of life".