How to read the contents of the sign?

How to read the contents of the sign?

PHP:

// imports
use pocketmine\math\Vector3;
use pocketmine\tile\Sign;
// code
/** @var \pocketmine\level\Level $level */
$sign = $level->getTile(new Vector3($x, $y, $z));
if($sign instanceof Sign){
    list($line1, $line2, $line3, $line4) = $sign->getText();
}

Thank you