admins_potential_selector.php

<?php
require_once($CFG->dirroot.'/user/selector/lib.php');

class admins_potential_selector extends user_selector_base {
    /**
     * @param string $name control name
     * @param array $options should have two elements with keys groupid and courseid.
     */
    public function __construct() {
        global $CFG, $USER;
        $admins = explode(',', $CFG->siteadmins);
        parent::__construct('addselect', array('multiselect'=>false, 'exclude'=>$admins));
    }

    public function find_users($search) {
        global $CFG, $DB;
        list($wherecondition, $params) = $this->search_sql($search, '');

        $fields      = 'SELECT ' . $this->required_fields_sql('');
        $countfields = 'SELECT COUNT(1)';

        $sql = " FROM {user}
                WHERE $wherecondition AND mnethostid = :localmnet AND username REGEXP '[a-zA-Z]'";
        $order = ' ORDER BY lastname ASC, firstname ASC';
        $params['localmnet'] = $CFG->mnet_localhost_id; // it could be dangerous to make remote users admins and also this could lead to other problems

        // Check to see if there are too many to show sensibly.
        if (!$this->is_validating()) {
            $potentialcount = $DB->count_records_sql($countfields . $sql, $params);
            if ($potentialcount > 100) {
                return $this->too_many_results($search, $potentialcount);
            }
        }

        $availableusers = $DB->get_records_sql($fields . $sql . $order, $params);

        if (empty($availableusers)) {
            return array();
        }

        if ($search) {
            $groupname = get_string('potusersmatching', 'role', $search);
        } else {
            $groupname = get_string('potusers', 'role');
        }

        return array($groupname => $availableusers);
    }

    protected function get_options() {
        global $CFG;
        $options = parent::get_options();
        $options['file'] = $CFG->admin . '/roles/lib.php';
        return $options;
    }

}