Paul writes to the Philippians in epistles from prison, he writes to them to thank them for their continued support and encouragement.
In Chapters 1-2: Paul writes about his sufferings, but writes that because of his sufferings the work of God has continued; “… I would ye should understand, brethren, that the things which happened unto me have fallen out rather unto the furtherance of the gospel.” (Philippians 1:12) As a follower of Jesus Christ, you often have to surrender your life to further the work of Christ’s kingdom on earth. For as a believer of Christ we have to not only have “…to believe on him, but also to suffer for his sake.” (Philippians 1:29)
Paul explains that because Jesus Christ suffered for us, God exalted Him on high, that “…every knee should bow…And…every tongue should confess that Jesus Christ is Lord…” (Philippians 2:10-11)
In Chapters 3-4: Paul expounds on the joys of being a Christian and encourages the church to press forward with the Gospel. Paul continues to explain how we can have joy in Jesus Christ, and that the believers will rejoice in Him when they are grounded in prayer and thanksgiving. He ends by explaining that whatsoever things are: true, honest, just, pure, lovely, virtuous and of good report , should be on the minds of the Saints who believe on Christ.