Paul prays that their love would “abound more and more” with knowledge and discernment: Philippians 1:9. He asks that they be pure and blameless for the day of Christ, filled with the fruit of righteousness through Jesus Christ: Philippians 1:10–11.
In Philippians 1:8–11, Paul swears that God can confirm how deeply he misses the Philippians, and he describes the emotional quality of that longing as coming through Christ. He then reports a focused prayer: that their love would keep growing, but in a way shaped by understanding and good judgment. This paragraph continues Paul’s opening thanksgiving and prayer section (1:3–11).
Paul’s prayer joins two ideas that are sometimes separated: strong affection and clear moral perception. He does not only say he loves them; he calls God as witness that his longing is real (verse 8). He also describes that longing as marked by the compassion associated with Christ—his relationship with them is not merely social warmth.
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with Philippians 1:9, then read the surrounding section so the answer stays connected to the passage's flow.
9This I pray, that your love may abound yet more and more in knowledge and all discernment;