Here Paul emphasizes how close the relationship is with the Christians in Philippi. He holds them all(!) in his heart. The partners in the gospel (Philippians 1:5) are also partakers in the grace that Paul received. By grace
Paul does not mean undeserved gifts such as redemption and the bond with Christ, but that he may be a proclaimer of the gospel. In other letters, too, he calls his apostleship such a gift (grace) from God (e.g., Romans 1:5; 1 Corinthians 3:10, Ephesians 3:2).
Perhaps Paul is referring here to his captivity by grace.
After all, he mentions it. Compare this with Philippians 1:29 where he uses a word for grace in connection with the suffering of the Philippians.
It is clear that the Christians in Philippi are not helping a pitiable prisoner, but an apostle who has received the grace to continue spreading the gospel as a prisoner. Through the help they give Paul, they cooperate with him in the defense and confirmation of the gospel. These words are reminiscent of a lawsuit. This is not about Paul’s lawsuit, but about the gospel that Paul had to defend. The gospel was also confirmed: it stood strong.
7 Il est juste que je pense ainsi de vous tous, parce que je vous porte dans mon cœur, soit dans mes liens, soit dans la défense et la confirmation de l'Evangile, vous qui tous participez à la même grâce que moi.