平滑重启，更新业务代码疑问

$worker = new Worker('websocket://127.0.0.1:9090');
$worker->onMessage = function($con, $data) {
    $con->send('hello');
}
Worker::runAll();

$worker = new Worker('websocket://127.0.0.1:9090');
$worker->onWorkerStart = function() {
    require 'app.php';
    $worker->onMessage = 'app_message';
}
Worker::runAll();

<?php
function app_message($con, $data) {
    $con->send('hi');
}