mysql_change_user() changes the logged in user of the current active connection, or the connection given by the optional link_identifier parameter. If a database is specified, this will be the current database after the user has been changed. If the new user and password authorization fails, the current connected user stays active. 成功回傳TRUE失敗回傳FALSE。
注: This deprecated function is only available in PHP 3 and requires MySQL 3.23.3 or higher.