Philippians has been full of personal updates and practical matters.  Paul now continues to give personal updates on two servants for Christ who demonstrate the ideals and characteristics that Paul had been encouraging in vv 1:27-2:18 .  Both Timothy and Epaphroditus have “served” Paul in his time of need, and Epaphroditus was even willing to lay down his life for the gospel message. 

It is not uncommon for Paul to give updates on others involved in sharing the gospel message.  But it is perhaps more common for them to occur at the end of a letter.