After upgrading from php 5.2 to php 5.3 on Windows, I was unable to connect to MySQL databases on localhost. I eventually tracked the problem down to entries in my hosts file:
Commenting out the second line fixed the problem.
The problem is explained here: http://bugs.php.net/bug.php?id=50172
This section provides a collection of miscellaneous notes on MySQL Native Driver usage.
Using mysqlnd means using PHP streams for underlying connectivity. For mysqlnd, the PHP streams documentation (Streams) should be consulted on such details as timeout settings, not the documentation for the MySQL Client Library.