Since you can't always be online when you need to install new libraries you'll need for your PHP work, Lorna Mitchell has posted a quick guide to downloading and installing PEAR packages when you're offline.

As with most tools that work really well, I know very little about PEAR. I mean, I use it all the time, and I love it for getting all the extensions installed that I need for the work I do. [...] However I'm now in a situation where I might need to install PEAR packages with a connection that may or may not be working, and I'm not sure exactly which packages I might need, so I wanted to know whether I could use PEAR as my packaging tool even when I wasn't able to reach the usual channels. And guess what? I can!

The install is a pretty simple two-step process - just download the package(s) you'll need for your development and point the PEAR installer (you'll need this installed first, obviously) at the archive file. It's smart enough to take care of the rest.