fetch security salt in cakephp 3

I read documents and I am not able to get it how to get Security.salt value from app.php in Cakephp 3. I am trying to get it like this

$salt = Configure::read('Security.salt');

Importing following libraries

use Cake\Core\Configure;
use Cake\Core\Configure\Engine\PhpConfig;

Kindly help.

Cakephp version is 3.4