PHP 5.3, using old authentication?

We're setting up a new webserver with PHP5.3 and are getting the "Error: could not connect: mysqlnd cannot connect to MySQL 4.1+ using old authentication ?" error message. After some google'ing I've found that we should set old passwords = 0 in my.cnf and reset the password(s). But we still have webservers running php 4.x & 5.2 that access the same mysql server (different users & databases), how will these be affected by this ? Will the mysql server be compatible with all the di开发者_如何学Gofferent PHP versions ?

The "new" model was introduced with MySQL 4.1 which is rather old so most of your systems most likely already use clients which understand the new way of handling authentication. You may also use different users with different models, after changing the old_passwords my.cnf setting you can set passwords using the OLD_PASSWORD() SQL function for clients older 4.1 and using PASSWORD() for clients 4.1 and older.

In general the old mechanism doesn't provide as strong security as the new one and the new way of handling logins is strongly preferred.