PEAR is a framework and distribution system for reusable PHP components. See Php - Archive (phar) - Package
The PEAR package manager can:
PEAR is normally installed with a newly php installation, check:
If not, See installation. Example on Windows with Powershell in Admin mode:
Give to the users group full permission on pear.ini
The require_once() function need the php_dir to be a part of PHP's include path.
Verification:
Check: System.php is shipped with every PEAR installation and must be discoverable:
Idea configuration for Pear.
Example with phpunit