Solved Get nearest player?

In terms of coding, how do I find the nearest player from the command executor??

Did you mean command sender/issuer?

PHP:

if($sender instanceof Position){ // if the sender is a position, for example a player
  $closest = null;
  $lastSquare = -1;
  foreach($sender->getLevel()->getPlayers() as $p){ // for every player in the sender's world
    if($p !== $sender){
      $square = $sender->distanceSquared($p); // get the square of the distance between the sender and the currently checking player
      // use distanceSquared() because it is faster than distance()
      if($lastSquare === -1 or $lastSquare > $square){ // this is the so far closest player
        $closest = $p;
        $lastSquare = $square;
      }
    }
  }
  // do something with $closest
  // $closest may be null if there are no players in the world except $sender
}

PHP:

foreach($p->getLevel()->getNearbyEntities(new AxisAlignedBB($pos->getX()-10, $pos->getY()-10, $pos->getZ()-10, $pos->getX()+10, $pos->getY()+10, $pos->getZ()+10), $p) as $entity)


is this function bad? @PEMapModder?

I want to teleport the sender to the closest player. I think I am only missing the teleportation. What value should I use?

Read the code I gave you and try to understand it. You are welcome to ask any questions about the code itself, but before you do, don't try to add it into your code.

I never even tried.

You are asking a question that you shouldn't be asking if you understand it. And asking this question shouldn't help you understanding it.
Anyway it is $closest