Wordpress is a php package, so it’s architecture independant and has hardly any dependencies. In fact the only dependency that can’t be satisfied from stable is libphp-phpmailer: wordpress 2.2 needs a newer version of this library than shipped with etch. It’s possible to manually download those two packages from the testing distribution and install them manually, but there’s a better way.

Add the testing distribution to your /etc/apt/sources.list so it looks like this (the first two should already be in there):

deb http://ftp.uk.debian.org/debian/ etch main contrib non-free
deb http://security.debian.org/ etch/updates main contrib non-free
deb http://ftp.uk.debian.org/debian/ testing main

Then use apt-pinning to disable the testing distribution for all packages except the ones you want. Edit the /etc/apt/preferences file (you may have to create it if it doesn’t already exist) so it looks like this:

Package: *
Pin: release a=stable
Pin-Priority: 700

Package: *
Pin: release a=testing
Pin-Priority: -1

Package: wordpress
Pin: release a=testing
Pin-Priority: 800

Package: libphp-phpmailer
Pin: release a=testing
Pin-Priority: 800

The magic part of this is the preference of “-1″ for the testing distribution, which removes its packages from the available list. If you put a positive preference such as 500 (which is lower than the stable preference of 700), stable will still “win” for most packages but you’ll see some that aren’t in stable. The preference of 800 is assigned to the two packages we *do* want, and this makes them preferred over stable.

Now install wordpress 2.2:

apt-get update
apt-get install wordpress

If you already have wordpress 2.0 installed, “apt-get update; apt-get upgrade” will upgrade your 2.0 copy instead.

This technique can be used to cherry pick other packages from testing into a stable base system, but only if they don’t have significant dependencies (such as a newer c library version). In this case, backports.org is your friend.