Client closed its connection

[mqttdeve]

Every few minutes mosquitto client close its connection and I need to restart my php code to subscribe again to the topic.

1641819601: New connection from 127.0.0.1:60140 on port 1883.
1641819601: New client connected from 127.0.0.1:60140 as auto-9249AABA-8610-21C7-6311 (p2, c1, k5).
1641819622: Client auto-9249AABA-8610-21C7-6311 closed its connection.

php code exit from disconnect function.

What causes this problem and How can I solve it?