PHP and mysqlnd
Ulf Wendel at Internet Super Hero has explained what the mysqlnd driver for PHP is and why you might (or might not) need it. He also provides a nice history of the drivers and APIs that PHP uses to connect to MySQL.
In short, mysqlnd is a MySQL native driver for PHP that works like libmysql. It’s a replacement for libmysql but they can co-exist so that it doesn’t break existing applications. Primarily, mysqlnd offers improved speed, persistent connections, mysqli_fetch_all() and performance statistics calls.
In my opinion, if you are using ext/mysqli then you’ll want to check it out and see if the feature/performance trade-offs make sense for you. It’s primarily designed for advanced users who need to get every drop of performance out of PHP that they can. If you are using PDO/MySQL then you’ll want to avoid it because PDO isn’t supported yet. If you are using ext/mysql for general use (or don’t know what “ext/mysql”, “ext/mysqli” and “PDO/MySQL” are) then stick with what you’ve got—you’ll never notice the difference.
