adding extension to apt-installed PHP

[alex at crackpot.org]

I'm running Debian testing/unstable.  I've recently upgraded to PHP 5.1 via apt.
 I'd like to start using PDO (PHP Data Objects, object-oriented database
abstraction), but I'm not sure how to get it installed/configured on my system.

PDO is included in the PHP 5.1 source :

"If you're running a PHP 5.1 release, PDO is included in the distribution; it
will be automatically enabled when you run configure. It is recommended that
you build PDO as a shared extension, as this will allow you to take advantage
of updates that are made available via PECL."
(http://www.php.net/manual/en/ref.pdo.php).

But : I don't see any mention of it on my system (in php.ini or by using
'locate'), so I'm thinking maybe it wasn't included in the version I got via
apt.  If that is right, is there a way to extend the version I have, or do I
need to start from scratch and compile my own PHP?  Since PDO can be installed
as a shared extension, is there a way to compile just the extension and then
link it into my existing PHP?

In a more general question, how can I find out how the PHP I have was compiled?

thanks!

alex