Need Help

I work on a mini game but I have a problem, can some one help me?
When player tap the sign, this player will teleport to (pos1)
when another player tap the sign, this player will teleport to (pos2)
them pos3, pos4
if the first player leave, the next player tap the sign will teleport to pos1

Got a Basic code?

make variable

PHP:

 public $pos = [1, 2, 3, 4, 5, 6, 7, 8]; 
public $players = [];

when player touch sign:

PHP:

$player->teleport(min($this->pos));
$this->players[strtolower($player->getName())] = min($this->pos);
unset(min($this->pos));


when player leave

PHP:

$pos[0]= $this->players[strtolower($player->getName())];
unset($this->players[strtolower($player->getName())];


i think it should work.

When player joins, push the position into another array and shift it out of the old array.
When player quits, pull out the relevant position and unshift it back into the old array.

No Really Understand:
I use another example please help me:

===========================

PHP:

public function playerJoinEvent(PlayerJoinEvent $event){
             if(!isset($this->players[$event->getPlayer()->getName()])){
            $this->players[$event->getPlayer()->getName()]=array("id"=>$event->getPlayer()->getName());
            }else{
         $event->getPlayer()->sendMessage("Error during this match");
         $event->getPlayer()->kick("Error", false);
       }
}
    public function PlayerQuit(PlayerQuitEvent $event){
        if(isset($this->players[$event->getPlayer()->getName()]))
        unset($this->players[$event->getPlayer()->getName()]);
        }  


For Example:
pos1 = 1,1,1,skywars;
pos2 = 2,2,2,skywars;
pos3 = 3,3,3,skywars;
pos4 = 4,4,4,skywars
So how to write?

PHP:

private $availableSpawns, $usedSpawns = []; // populate $availableSpawns yourself
private function join(Player $player){
  $pos = array_shift($this->availableSpawns); // extract one from available list
  $this->usedSpawns[$player->getId()] = $pos; // add it into used list
  $player->teleport($pos);
}
private function quit(Player $player){
  if(isset($this->usedSpawns[$player->getId()])){
    $pos = $this->usedSpawns[$player->getId()];
    unset($this->usedSpawns[$player->getId()]); // remove it from used list
    array_unshift($this->availableSpawns, $pos); // put it back into available list
  }
}

So when player join :
$this->join($player);
Quit:
$this->quit($player);

And what should I write in $usedSpawns = [ HERE ]

Learn PHP... This is the syntax for an array.

I mean should I put the pos & level or v3 in side...

You can't populate objects at that context. Populate the array in somewhere like onEnable or when your arena starts.