If you wish to install Pear on the cPanel server, then you can use the standard way provided by WHM/cPanel. However, if you use the alt-PHP (PHP Selector), then you can install the required PEAR packages the following way:
# /opt/alt/phpXX/usr/bin/pear install moduleName
where XX is PHP version (e.g., 71 for PHP 7.1).
In this case, the include_path will contain the value "/opt/alt/php71/usr/share/pear"
Alternatively, you can set it manually in /opt/alt/php71/etc/php.ini directly (PHP 7.1 as an example):
include_path = ".:/usr/share/pear:/opt/alt/php71/usr/share/php:/opt/alt/php71/usr/share/pear"