Create a countdown

Hi, I need to create a countdown I have started this but its not work.

----
$this->getServer()->getScheduler()->scheduleDelayedTask(new class($this) extends PluginTask{
public function onRun(int $currentTick){
}
}, 20 * 10);
----

 

PHP:

Server::getInstance()->getScheduler()->scheduleDelayedTask(new class($this, 10) extends Task{
                   
                    public function __construct($pl, $time){
                        $this->pl = $pl;
                        $this->time = $time;
                    }
                   
                    public function onRun($timer){
            $time = $this->time--;
//$time
                    }
                }, 4);


 

Thank you, i set this in a new file.php?

 

not, insert the Main Class