What does Philippians 1:27 mean?

No matter what happens, live in a way that matches the good news about Christ. Then, whether I come see you or just hear about you, I’ll know you’re standing strong together, united by your trust in the message. Philippians 1:27 - Modern Text Bible

(Paul urges them to live lives worthy of the gospel, showing unity and steadfastness whether he visits or not.)