What does Acts 19:22 mean?

This is the first time we hear that Paul had anyone accompanying him during his third missionary voyage. This is also the first we hear of Erastus. In Romans 16:23, which Paul writes from Ephesus, Paul calls him "the city treasurer"; if this is the same man, it's interesting he is at liberty to travel to Macedonia for Paul.

Paul spends about three years in Ephesus (Acts 20:31). He doesn't travel too much around the province of Asia, in southwest modern-day Turkey, because Epaphras started the churches in Colossae, Laodicea, and Hierapolis (Colossians 1:7–8; 2:1; 4:12–14). He is making plans to sail west to Corinth, then north through Macedonia. Unfortunately, he hears troubling news about the church in Corinth. It's possible this news is about the church splitting up and following different leaders, combined with a church member living in blatant sin (1 Corinthians 1:10–17; 3:1–23; 5:1–8). We're not sure, however, because Paul apparently wrote four letters to Corinth; only the second and fourth are part of preserved Scripture.

Whatever the problem, Paul writes a very strongly worded letter to Corinth and sends it with Titus (2 Corinthians 7:6–7, 13). Titus is barely out of sight before Paul regrets his decision (2 Corinthians 7:8–9). Soon, a near-riot will convince him to leave Ephesus (Acts 19:23—20:1). He decides to go to Macedonia first, so he travels north to the port of Troas and sails to Philippi. When Titus doesn't meet him in Troas, Paul is nearly overcome with anxiety (2 Corinthians 2:12–13). He finally finds Titus in Macedonia and learns the good news that the Corinthians have humbly repented (2 Corinthians 7:5–9). He goes south to Corinth where he stays three months before he's forced to backtrack through Macedonia and Troas (Acts 20:2–6).