PEAR
PEAR (PHP Extension and Application Repository) is a framework and distribution system for reusable PHP components. It provides a structured library of open-source code for PHP developers to easily install, upgrade, and manage packages. PEAR includes both a command-line tool for package management and a collection of packages covering common tasks like database access, authentication, and templating.
Developers should learn PEAR when working on legacy PHP projects or maintaining systems built before modern dependency managers like Composer became standard. It's useful for managing reusable components in PHP 4 and early PHP 5 applications, providing a centralized repository and installation system. However, for new projects, Composer is now the recommended tool due to better dependency resolution and wider adoption.