如何在我的类文件中使用我的DEFINE var文件并在课堂中使用？ 用PHP

i have config.php file

<?php 
define(DBHOST, 'localhost');
define(DBNAME, 'new_shop_site');
define(DBUSER, 'root');
define(DBPASS, '');
 ?>

i try to get value of thes file in my database.php file

database.php i try 1

<?php 
    class database{
include_once("config/config.php");
        /*database credentials*/

        private static $host = DBHOST;
        private static $username = DBUSER;
        private static $pass = DBPASS;
        private static $dbname = DBNAME;
}
?>

then try 2

<?php 
include_once("config/config.php");
    class database{
        /*database credentials*/

        private static $host = DBHOST;
        private static $username = DBUSER;
        private static $pass = DBPASS;
        private static $dbname = DBNAME;
}
?>

but not working. how i get this value?