Fatal error: Uncaught exception ‘PDOException’ with message ‘SQLSTATE[HY000] [2000] 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’ in /home/hailong.xhl/test.php:8
mysqlnd是个好东西。不仅可以提高与mysql数据库通信的效率，而且也可以方便的设置一些超时。如，连接超时，查询超时。
但是，使用mysqlnd的时候，有个地方需要注意。就是服务端的密码格式不能使用旧的16位的存储格式，而要使用新的41位的存储格式。
查看自己的密码是否符合要求
mysql> select user,host,length(password) from mysql.user; +-----------+-----------+------------------+ | user | host | length(password) | +-----------+-----------+------------------+ | root | localhost | 0 | | demo | % | 16| | root | 127.0.0.1 | 0 | | | root | 192.168.% | 16 | | |
上面的密码是旧的16位格式。如果想改成新的41位格式，通过以下命令就可以
mysql> set old_passwords=0;
mysql> update mysql.user set Password = PASSWORD("demo") where user="demo";
mysql> select user,length(password) from mysql.user;
+--------------+------------------+
| user | length(password) |
+--------------+------------------+
| demo | 41 |
| demo | 41 |
+--------------+------------------+
mysql> flush privileges修改完密码后，还需要在配置文件中修改下old_passwords选项。把值设置为0
mysqlnd cannot connect to MySQL 4.1+ using the old insecure authentication解决办法
原文：http://dihuo.blog.51cto.com/1657091/1622559