PEAR

PEAR (http://pear.php.net/) is the PHP Extension and Add-on Repository.

It's a glue framework, meaning it contains independent packages that can be chosen and "glued" together in your application to meet your requirements. Since PEAR dates back to the origins of PHP, it is oftentimes an underlying requirement for basic PHP functionality which other developers build upon. For a hypothetical example, you could have a Drupal module developer use an underlying PEAR package for critical functionality at the system level, while the module proper deals with application integration and extension of Drupal capabilities.

PEAR is also a packaging and code distribution system using a command-line application (think apt-get). There is actually a web front-end available too for managing PEAR packages. See http://blog.jldupont.com/2008/03/pear-web-installer.html for more on that.

Notable PEAR developers:

Brion Vibber (CTO of MediaWiki Foundation)
Jean-Lou Dupont
Gregory Beaver

PEAR in 2016

Is PEAR still relevant? In the age of GitHub and Composer, if you listen to chatter on the Internet, it's easy to think that PEAR is a moribund project that is also irrelevant. But it is actually alive and kicking. Sadly, I don't think that the trends will reverse. Still, you need to know about PEAR and even how to use it with idempotency in Ansible.