here done is a common field, which is actually the same as the following, which is the basic usage of PHP:

class A {
}

$a = new A();
$a->done = true;

Run

your complete code should be an example in pthread:

<?php
class My extends Thread {
    public function run() {
        $this->synchronized(function($thread){
            if (!$thread->done)
                $thread->wait();
        }, $this);
    }
}
$my = new My();
$my->start();
$my->synchronized(function($thread){
    $thread->done = true;
    $thread->notify();
}, $my);
var_dump($my->join());

start () starts running run () in the child thread, which is done has not yet been assigned, so wait () will be executed. The main thread then executes notofy () to wake up the child threads that are wait () .

another case is that the main thread first assigns and executes notify () to done , and then executes run () to the child thread. At this time, the child thread does not need wait , because the main thread is already notify () .