PEAR (short for PHP Extension and Application Repository) is a framework and distribution system for reusable PHP components. In includes many useful tools and components that can be easily downloaded and installed by using PEAR package manager. This post describes how to install and configure PEAR package manager and then how to use it to install a PEAR package. An example PEAR package used in this post is phploc, which is a tool for measuring the size of PHP projects.
He recommends installing PHP via the Web Platform Installer and use the PHP 5.3 VC9 non-thread-safe package with the PHP Manager. All of the commands needed are included as well as some of the sample output that results. Once you get PEAR installed, then they show how to discover the PEAR channel and "pear install" the right packages for phploc (including the dependencies it might need).