//.........这里部分代码省略.........
            if (!isset($forums[$forumid])) {
                if ($forum = $DB->get_record('forum', array('id' => $forumid))) {
                    $forums[$forumid] = $forum;
                } else {
                    mtrace('Could not find forum '.$forumid);
                    unset($posts[$pid]);
                    continue;
                }
            }
            $courseid = $forums[$forumid]->course;
            if (!isset($courses[$courseid])) {
                if ($course = $DB->get_record('course', array('id' => $courseid))) {
                    $courses[$courseid] = $course;
                } else {
                    mtrace('Could not find course '.$courseid);
                    unset($posts[$pid]);
                    continue;
                }
            }
            if (!isset($coursemodules[$forumid])) {
                if ($cm = get_coursemodule_from_instance('forum', $forumid, $courseid)) {
                    $coursemodules[$forumid] = $cm;
                } else {
                    mtrace('Could not find course module for forum '.$forumid);
                    unset($posts[$pid]);
                    continue;
                }
            }


            // caching subscribed users of each forum
            if (!isset($subscribedusers[$forumid])) {
                $modcontext = context_module::instance($coursemodules[$forumid]->id);
                if ($subusers = forum_subscribed_users($courses[$courseid], $forums[$forumid], 0, $modcontext, "u.*")) {
                    foreach ($subusers as $postuser) {
                        // this user is subscribed to this forum
                        $subscribedusers[$forumid][$postuser->id] = $postuser->id;
                        $userscount++;
                        if ($userscount > FORUM_CRON_USER_CACHE) {
                            // Store minimal user info.
                            $minuser = new stdClass();
                            $minuser->id = $postuser->id;
                            $users[$postuser->id] = $minuser;
                        } else {
                            // Cache full user record.
                            forum_cron_minimise_user_record($postuser);
                            $users[$postuser->id] = $postuser;
                        }
                    }
                    // Release memory.
                    unset($subusers);
                    unset($postuser);
                }
            }

            $mailcount[$pid] = 0;
            $errorcount[$pid] = 0;
        }
    }

    if ($users && $posts) {

        $urlinfo = parse_url($CFG->wwwroot);
        $hostname = $urlinfo['host'];

        foreach ($users as $userto) {

    } else {
        if (!empty($frm->remove) and !empty($frm->removeselect)) {
            foreach ($frm->removeselect as $removesubscriber) {
                if (!forum_unsubscribe($removesubscriber, $id)) {
                    print_error('cannotremovesubscriber', 'forum', '', $removesubscriber);
                }
            }
        } else {
            if (!empty($frm->showall)) {
                $searchtext = '';
            }
        }
    }
}
/// Get all existing subscribers for this forum.
if (!($subscribers = forum_subscribed_users($course, $forum, $currentgroup, $context))) {
    $subscribers = array();
}
/// Get all the potential subscribers excluding users already subscribed
$users = forum_get_potential_subscribers($context, $currentgroup, 'id,email,firstname,lastname', 'firstname ASC, lastname ASC');
if (!$users) {
    $users = array();
}
foreach ($subscribers as $subscriber) {
    unset($users[$subscriber->id]);
}
/// This is yucky, but do the search in PHP, becuase the list we are using comes from get_users_by_capability,
/// which does not allow searching in the database. Fortunately the list is only this list of users in this
/// course, which is normally OK, except on the site course of a big site. But before you can enter a search
/// term, you have already seen a page that lists everyone, since this code never does paging, so you have probably
/// already crashed your server if you are going to. This will be fixed properly for Moodle 2.0: MDL-17550.

 /**
  * Test subscription using disallow subscription on create.
  */
 public function test_forum_disallow_subscribe_on_create()
 {
     global $CFG;
     $this->resetAfterTest();
     $usercount = 5;
     $course = $this->getDataGenerator()->create_course();
     $users = array();
     for ($i = 0; $i < $usercount; $i++) {
         $user = $this->getDataGenerator()->create_user();
         $users[] = $user;
         $this->getDataGenerator()->enrol_user($user->id, $course->id);
     }
     $options = array('course' => $course->id, 'forcesubscribe' => FORUM_DISALLOWSUBSCRIBE);
     // Subscription prevented.
     $forum = $this->getDataGenerator()->create_module('forum', $options);
     $result = forum_subscribed_users($course, $forum);
     // No subscriptions by default.
     $this->assertEquals(0, count($result));
     foreach ($users as $user) {
         $this->assertFalse(forum_is_subscribed($user->id, $forum));
     }
 }

/**
 * Function to be run periodically according to the moodle cron
 * Finds all posts that have yet to be mailed out, and mails them
 * out to all subscribers
 * @return void
 */
function forum_cron()
{
    global $CFG, $USER;
    $cronuser = clone $USER;
    $site = get_site();
    // all users that are subscribed to any post that needs sending
    $users = array();
    // status arrays
    $mailcount = array();
    $errorcount = array();
    // caches
    $discussions = array();
    $forums = array();
    $courses = array();
    $coursemodules = array();
    $subscribedusers = array();
    // Posts older than 2 days will not be mailed.  This is to avoid the problem where
    // cron has not been running for a long time, and then suddenly people are flooded
    // with mail from the past few weeks or months
    $timenow = time();
    $endtime = $timenow - $CFG->maxeditingtime;
    $starttime = $endtime - 48 * 3600;
    // Two days earlier
    if ($posts = forum_get_unmailed_posts($starttime, $endtime, $timenow)) {
        // Mark them all now as being mailed.  It's unlikely but possible there
        // might be an error later so that a post is NOT actually mailed out,
        // but since mail isn't crucial, we can accept this risk.  Doing it now
        // prevents the risk of duplicated mails, which is a worse problem.
        if (!forum_mark_old_posts_as_mailed($endtime)) {
            mtrace('Errors occurred while trying to mark some posts as being mailed.');
            return false;
            // Don't continue trying to mail them, in case we are in a cron loop
        }
        // checking post validity, and adding users to loop through later
        foreach ($posts as $pid => $post) {
            $discussionid = $post->discussion;
            if (!isset($discussions[$discussionid])) {
                if ($discussion = get_record('forum_discussions', 'id', $post->discussion)) {
                    $discussions[$discussionid] = $discussion;
                } else {
                    mtrace('Could not find discussion ' . $discussionid);
                    unset($posts[$pid]);
                    continue;
                }
            }
            $forumid = $discussions[$discussionid]->forum;
            if (!isset($forums[$forumid])) {
                if ($forum = get_record('forum', 'id', $forumid)) {
                    $forums[$forumid] = $forum;
                } else {
                    mtrace('Could not find forum ' . $forumid);
                    unset($posts[$pid]);
                    continue;
                }
            }
            $courseid = $forums[$forumid]->course;
            if (!isset($courses[$courseid])) {
                if ($course = get_record('course', 'id', $courseid)) {
                    $courses[$courseid] = $course;
                } else {
                    mtrace('Could not find course ' . $courseid);
                    unset($posts[$pid]);
                    continue;
                }
            }
            if (!isset($coursemodules[$forumid])) {
                if ($cm = get_coursemodule_from_instance('forum', $forumid, $courseid)) {
                    $coursemodules[$forumid] = $cm;
                } else {
                    mtrace('Could not course module for forum ' . $forumid);
                    unset($posts[$pid]);
                    continue;
                }
            }
            // caching subscribed users of each forum
            if (!isset($subscribedusers[$forumid])) {
                if ($subusers = forum_subscribed_users($courses[$courseid], $forums[$forumid], 0, false)) {
                    foreach ($subusers as $postuser) {
                        // do not try to mail users with stopped email
                        if ($postuser->emailstop) {
                            if (!empty($CFG->forum_logblocked)) {
                                add_to_log(SITEID, 'forum', 'mail blocked', '', '', 0, $postuser->id);
                            }
                            continue;
                        }
                        // this user is subscribed to this forum
                        $subscribedusers[$forumid][$postuser->id] = $postuser->id;
                        // this user is a user we have to process later
                        $users[$postuser->id] = $postuser;
                    }
                    unset($subusers);
                    // release memory
                }
            }
//.........这里部分代码省略.........

        }
    }
    $subscriberselector->invalidate_selected_users();
    $existingselector->invalidate_selected_users();
    $subscriberselector->set_existing_subscribers($existingselector->find_users(''));
}
$strsubscribers = get_string("subscribers", "forum");
$PAGE->navbar->add($strsubscribers);
$PAGE->set_title($strsubscribers);
$PAGE->set_heading($COURSE->fullname);
if (has_capability('mod/forum:managesubscriptions', $context)) {
    $PAGE->set_button(forum_update_subscriptions_button($course->id, $id));
    if ($edit != -1) {
        $USER->subscriptionsediting = $edit;
    }
} else {
    unset($USER->subscriptionsediting);
}
echo $OUTPUT->header();
echo $OUTPUT->heading(get_string('forum', 'forum') . ' ' . $strsubscribers);
if (empty($USER->subscriptionsediting)) {
    echo $forumoutput->subscriber_overview(forum_subscribed_users($course, $forum, $currentgroup, $context), $forum, $course);
} else {
    if (forum_is_forcesubscribed($forum)) {
        $subscriberselector->set_force_subscribed(true);
        echo $forumoutput->subscribed_users($subscriberselector);
    } else {
        echo $forumoutput->subscriber_selection_form($existingselector, $subscriberselector);
    }
}
echo $OUTPUT->footer();