Particles

Is there a way to spawn particles only for some players or something like that?

 

Yes,
\pocketmine\level addParticle(Particle $particle, array $players).

When calling the function, build an array with only the players you want to send the particle to. For example, if you want to only send particles to players with a certain permission try this:

PHP:

$players = array();
/** $player instanceof Player */
if($player->hasPermission("example.permission")){
    array_push($players, $player);
}

/** Assuming $particle is set */
$player->getLevel()->addParticle($particle, $players);