main.php

<?php

use pocketmine\scheduler\Task;
class Main extends PluginBase implements Listener{
  
  public function onEnable(){
    $this->getServer()->getPluginManager()->registerEvents($this, $this);
  }
  
  public function onJoin(PlayerJoinEvent $ev){
    $player = $ev->getPlayer();
    $this->getServer()->getScheduler()->scheduleDelayedTask(new CallbackTask([$this, "test"], [$player]), 1);
  }
  
  public function test($player){
    $player->sendMessage("ようこそ");
  }
}

class CallbackTask extends Task {
	protected $callable, $args;
	/**
	 * @param callable $callable
	 * @param array    $args
	 */
	public function __construct(callable $callable, array $args = [])
	{
		$this->callable = $callable;
		$this->args = $args;
		$this->args[] = $this;
	}
	/**
	 * @return callable
	 */
	public function getCallable() : callable
	{
		return $this->callable;
	}
	/**
	 * @param $currentTick
	 */
	public function onRun(int $currentTick)
	{
		call_user_func_array($this->callable, $this->args);//関数呼び出し
	}
}