XD you forgot an ; the above the latest line ( PHP: $event->$player->$pos->setBlock(new Vector3($x, $y, $z), Block::get(0))//add ; )
Yes it has to be PHP: $pos->setBlock(new Vector3($player->getFloorX(), $player->getFloorY() -1, $player->getFloorZ), Block::get(0)); instead of PHP: $event->$player->$pos->setBlock(new Vector3($x, $y, $z), Block::get(0)) the $x, $y ,$z variables were undefined..
Please don't post if you don't know what you are doing. We don't need somebody who copies and pastes code, and sometimes creates something that is entirely wrong.
EDIT: LOL? $event->$player->$pos... use PHP: $event->getPlayer()->getLevel()->setBlock($event->getBlock()->getPosition(),Block::get(0));