What's the easiest way to install PDO on the default php installation of OS X Leopard? I'm trying to get ModX running.
It can be a hassle to build PHP extensions with the Leopard default PHP. If you are just doing development work, look into MAMP, which has a whole bunch of extensions (including PDO for MySQL and PostgreSQL) built-in. It includes its own copy of Apache so you won’t be using the OS X default Apache. Don’t worry, there’s no installation needed.
A second option is Mark Liyanage’s PHP package which is a PHP module that you use instead of the one that comes with Leopard, but has a lot of extensions built-in.
MAMP is easier, but Liyanage’s package works with the built-in web server.
If you're looking for something that's a little bit more robust than MAMP, I'd recommend Zend Server Community Edition. It's similar to MAMP, but gives you more control over your server environment.