The text of Philippians is preserved in three fragmentary papyri, 18 parchment uncials (of which nine contain the entire text, three are fragmentary, and six are accompanied by commentary), and more than 625 minuscules (cf. Gnilka, 25–27). The earliest is P46, one of the three Chester Beatty papyri of the NT. It dates from about C.E. 200 and contains 1:1, 5–15, 17–28, 30–2:12, 14–27, 29–3:8, 10–21; 4:2–12, 14–23. A second early papyrus is P16, which dates from the 3d or 4th century and contains 3:10–17 and 4:2–8. The three earliest parchment uncials that contain the entire text of Philippians are Codex Sinaiticus (01), Codex Vaticanus (03), and Codex Alexandrinus (02). These five mss, plus three minuscules containing Philippians (33, 1739, and 2427), belong to the text critical “Category I,” which indicates that they are “of a very special quality” and “should always be considered in establishing the original text” (Aland and Aland 1987: 105). There are ten additional manuscripts of Philippians that are of generally high quality and belong to the next class, “Category II” (Schenk 1984: 331). They include three 5th-century fragmentary uncials (04, 016, 048), the bilingual Codex Claromontanus (06, 6th century), P61 (ca. C.E. 700) and 5 minuscules (81, 1175, 1881, 2127, and 2464). On the basis of these and other witnesses, a fairly reliable text of Philippians which involves no major textual problems can be reconstructed.”
John T. Fitzgerald, author, editor Freedman, D. N. (1996). Vol. 5: The Anchor Yale Bible Dictionary (324). New York: Doubleday.
That makes the text of Philippians sound uncommonly secure. But that’s not to say we don’t have textual problems in Philippians. Philip Comfort spends sixteen pages on Philippians in his New Testament Text and Translation Commentary.