drupal_hash_salt global removed

$GLOBALS['drupal_hash_salt'] has been moved to the settings object and renamed to hash_salt.

D7

// NOT recommended: Retrieving hash salt directly from global
global $drupal_hash_salt; 

// Recommended: using drupal_get_hash_salt() 
$hash_salt = drupal_get_hash_salt();

D8

use Drupal\Core\Site\Settings;

// Not recommended: Retrieve hash salt using the get() function.
$hash_salt = Settings::get('hash_salt');
// Recommended: Using the getHashSalt() instead
$hash_salt = Settings::getHashSalt();