How do I use the PHP SDK without command line access to install the package.xml file with Pear?

Pear provides an easy way to install functionality and extend PHP. Unfortunately, many modules require you to have access to the command line, or to install modules directly to the Pear directory. Many web hosting companies don't provide this level of access, as the Pear directory is generally a shared directory for all accounts on the server.

Fortunately, you can install Pear packages without needing command-line access.