PHP mysqlnd cannot connect to MySQL 4.1+ using old authentication

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

SQLSTATE[HY000] [2000] mysqlnd cannot connect to MySQL 4.1+ using old authentication 

After struggling a while on google, I cannot find any solution. So I went back to the RTFM idiomatic expression.

It is what I found:

• php 5.3 now use a native extension to use mysql : mysqlnd
• my database credential was old (4 years old maybe) and still use the old mysql authentication
• mysqlnd needs the new 41bytes password

解决办法：

• Remove or comment old_passwords = 1 in my.cnf

Restart MySQL. If you don’t, MySQL will keep using the old password format, which will mean that you cannot upgrade the passwords using the builtin PASSWORD() hashing function.

The old password hashes are 16 characters, the new ones are 41 characters.

• Connect to the database, and run the following query:

  SELECT user, Length(Password) FROM mysql.user;

This will show you which passwords are in the old format, ex:

+----------+--------------------+ | user     | Length(`Password`) | +----------+--------------------+ | root     |                 41 | | root     |                 16 | | user2    |                 16 | | user2    |                 16 | +----------+--------------------+

Notice here that each user can have multiple rows (one for each different host specification).

To update the password for each user, run the following:

UPDATE mysql.user SET Password = PASSWORD('password') WHERE user = 'username';

Finally, flush privileges:

FLUSH PRIVILEGES;