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(来源 www.pms.cc)

解决方法如下，PASSWORD里面的是密码：

SET old_passwords = 0; 

UPDATE mysql.user SET Password = PASSWORD('www.pms.cc') WHERE User = 'pms' limit 1; 

SELECT LENGTH(Password) FROM mysql.user WHERE User = 'pms'; 

FLUSH PRIVILEGES;