settings.php

<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

// Written at Louisiana State University.

defined('MOODLE_INTERNAL') || die;

if ($ADMIN->fulltree) {
    require_once($CFG->dirroot . '/blocks/quickmail/lib.php');

    $select = array(0 => get_string('no'), 1 => get_string('yes'));

    $roles = $DB->get_records('role', null, 'sortorder ASC');

    $default_sns = array('editingteacher', 'teacher', 'student');
    $defaults = array_filter($roles, function ($role) use ($default_sns) {
        return in_array($role->shortname, $default_sns);
    });

    $only_names = function ($role) { return $role->shortname; };

    $select_roles = quickmail::_s('select_roles');
    $settings->add(
        new admin_setting_configmultiselect('block_quickmail_roleselection',
            $select_roles, $select_roles,
            array_keys($defaults),
            array_map($only_names, $roles)
        )
    );

    $settings->add(
        new admin_setting_configselect('block_quickmail_receipt',
        quickmail::_s('receipt'), quickmail::_s('receipt_help'),
        0, $select
        )
    );

    $options = array(
        0 => get_string('none'),
        'idnumber' => get_string('idnumber'),
        'shortname' => get_string('shortname')
    );

    $settings->add(
        new admin_setting_configselect('block_quickmail_prepend_class',
            quickmail::_s('prepend_class'), quickmail::_s('prepend_class_desc'),
            0, $options
        )
    );
}