You have to install PEAR and any modules manually into directories in your own account. They do not have to be under public_html.
You then have to adjust the include path by using code like:
$inc_path = get_include_path();
set_include_path($inc_path . ':/home/username/php_mail');
require_once "Mail.php";
where Mail.php is a PEAR module I installed (along with the modules that comprise PEAR)
The modules you want cannot use functions that x10 has disabled. x10 will not enable them for you.