I solved the problem like this. Created 2 user, and for all one password. And these three user has access to one database.
$style_class = array("new_user1","new_user2");
$random_class = array_rand($style_class, 1);
$div_class = $style_class[$random_class];
define('QA_MYSQL_HOSTNAME', 'localhost'); // try '127.0.0.1' or 'localhost' if MySQL on same server
define('QA_MYSQL_USERNAME', $div_class);
define('QA_MYSQL_PASSWORD', 'pass');
define('QA_MYSQL_DATABASE', 'dbname');