在万网虚拟主机上连接数据库出错mysqlnd cannot connect to MySQL 4.1+ using the old insecure authentication

PHP网站上传到万网的虚拟空间后，按照万网提供的数据库连接信息，但是却一直连不上数据库。后来，我直接写了个只包含数据库连接的简单PHP文件，运行，才得到完整的报错信息：

mysqlnd cannot connect to MySQL 4.1+ using the old insecure authentication. Please use an administration tool to reset your password with the command SET PASSWORD = PASSWORD('your_existing_password'). This will store a new, and more secure, hash value in mysql.user. If this user is used in other scripts executed by PHP 5.2 or earlier you might need to remove the old-passwords flag from your my.cnf file

经搜索，找到了解决的办法，通过navicat for mysql连接数据库，在命令行执行下面的语句：
SET SESSION old_passwords = FALSE;
SET PASSWORD = PASSWORD('your existing password in plain text');

再次运行连接数据库的脚本，能够正常连接数据库了。
另外，万网的IIS竟然不支持PHP 函数empty。