/**
     * Add a new discussion into an existing forum.
     *
     * @param int $forumid the forum instance id
     * @param string $subject new discussion subject
     * @param string $message new discussion message (only html format allowed)
     * @param int $groupid the user course group
     * @param array $options optional settings
     * @return array of warnings and the new discussion id
     * @since Moodle 3.0
     * @throws moodle_exception
     */
    public static function add_discussion($forumid, $subject, $message, $groupid = -1, $options = array()) {
        global $DB, $CFG;
        require_once($CFG->dirroot . "/mod/forum/lib.php");

        $params = self::validate_parameters(self::add_discussion_parameters(),
                                            array(
                                                'forumid' => $forumid,
                                                'subject' => $subject,
                                                'message' => $message,
                                                'groupid' => $groupid,
                                                'options' => $options
                                            ));
        // Validate options.
        $options = array(
            'discussionsubscribe' => true
        );
        foreach ($params['options'] as $option) {
            $name = trim($option['name']);
            switch ($name) {
                case 'discussionsubscribe':
                    $value = clean_param($option['value'], PARAM_BOOL);
                    break;
                default:
                    throw new moodle_exception('errorinvalidparam', 'webservice', '', $name);
            }
            $options[$name] = $value;
        }

        $warnings = array();

        // Request and permission validation.
        $forum = $DB->get_record('forum', array('id' => $params['forumid']), '*', MUST_EXIST);
        list($course, $cm) = get_course_and_cm_from_instance($forum, 'forum');

        $context = context_module::instance($cm->id);
        self::validate_context($context);

        // Normalize group.
        if (!groups_get_activity_groupmode($cm)) {
            // Groups not supported, force to -1.
            $groupid = -1;
        } else {
            // Check if we receive the default or and empty value for groupid,
            // in this case, get the group for the user in the activity.
            if ($groupid === -1 or empty($params['groupid'])) {
                $groupid = groups_get_activity_group($cm);
            } else {
                // Here we rely in the group passed, forum_user_can_post_discussion will validate the group.
                $groupid = $params['groupid'];
            }
        }

        if (!forum_user_can_post_discussion($forum, $groupid, -1, $cm, $context)) {
            throw new moodle_exception('cannotcreatediscussion', 'forum');
        }

        $thresholdwarning = forum_check_throttling($forum, $cm);
        forum_check_blocking_threshold($thresholdwarning);

        // Create the discussion.
        $discussion = new stdClass();
        $discussion->course = $course->id;
        $discussion->forum = $forum->id;
        $discussion->message = $params['message'];
        $discussion->messageformat = FORMAT_HTML;   // Force formatting for now.
        $discussion->messagetrust = trusttext_trusted($context);
        $discussion->itemid = 0;
        $discussion->groupid = $groupid;
        $discussion->mailnow = 0;
        $discussion->subject = $params['subject'];
        $discussion->name = $discussion->subject;
        $discussion->timestart = 0;
        $discussion->timeend = 0;

        if ($discussionid = forum_add_discussion($discussion)) {

            $discussion->id = $discussionid;

            // Trigger events and completion.

            $params = array(
                'context' => $context,
                'objectid' => $discussion->id,
                'other' => array(
                    'forumid' => $forum->id,
                )
            );
            $event = \mod_forum\event\discussion_created::create($params);
//.........这里部分代码省略.........

echo $OUTPUT->header();
echo $OUTPUT->heading(format_string($forum->name), 2);
// checkup
if (!empty($parent) && !forum_user_can_see_post($forum, $discussion, $post, null, $cm)) {
    print_error('cannotreply', 'forum');
}
if (empty($parent) && empty($edit) && !forum_user_can_post_discussion($forum, $groupid, -1, $cm, $modcontext)) {
    print_error('cannotcreatediscussion', 'forum');
}
if ($forum->type == 'qanda' && !has_capability('mod/forum:viewqandawithoutposting', $modcontext) && !empty($discussion->id) && !forum_user_has_posted($forum->id, $discussion->id, $USER->id)) {
    echo $OUTPUT->notification(get_string('qandanotify', 'forum'));
}
// If there is a warning message and we are not editing a post we need to handle the warning.
if (!empty($thresholdwarning) && !$edit) {
    // Here we want to throw an exception if they are no longer allowed to post.
    forum_check_blocking_threshold($thresholdwarning);
}
if (!empty($parent)) {
    if (!($discussion = $DB->get_record('forum_discussions', array('id' => $parent->discussion)))) {
        print_error('notpartofdiscussion', 'forum');
    }
    forum_print_post($parent, $discussion, $forum, $cm, $course, false, false, false);
    if (empty($post->edit)) {
        if ($forum->type != 'qanda' || forum_user_can_see_discussion($forum, $discussion, $modcontext)) {
            $forumtracked = forum_tp_is_tracked($forum);
            $posts = forum_get_all_discussion_posts($discussion->id, "created ASC", $forumtracked);
            forum_print_posts_threaded($course, $cm, $forum, $discussion, $parent, 0, false, $forumtracked, $posts);
        }
    }
} else {
    if (!empty($forum->intro)) {

    /**
     * Create new posts into an existing discussion.
     *
     * @param int $postid the post id we are going to reply to
     * @param string $subject new post subject
     * @param string $message new post message (only html format allowed)
     * @param array $options optional settings
     * @return array of warnings and the new post id
     * @since Moodle 3.0
     * @throws moodle_exception
     */
    public static function add_discussion_post($postid, $subject, $message, $options = array()) {
        global $DB, $CFG, $USER;
        require_once($CFG->dirroot . "/mod/forum/lib.php");

        $params = self::validate_parameters(self::add_discussion_post_parameters(),
                                            array(
                                                'postid' => $postid,
                                                'subject' => $subject,
                                                'message' => $message,
                                                'options' => $options
                                            ));
        // Validate options.
        $options = array(
            'discussionsubscribe' => true
        );
        foreach ($params['options'] as $option) {
            $name = trim($option['name']);
            switch ($name) {
                case 'discussionsubscribe':
                    $value = clean_param($option['value'], PARAM_BOOL);
                    break;
                default:
                    throw new moodle_exception('errorinvalidparam', 'webservice', '', $name);
            }
            $options[$name] = $value;
        }

        $warnings = array();

        if (!$parent = forum_get_post_full($params['postid'])) {
            throw new moodle_exception('invalidparentpostid', 'forum');
        }

        if (!$discussion = $DB->get_record("forum_discussions", array("id" => $parent->discussion))) {
            throw new moodle_exception('notpartofdiscussion', 'forum');
        }

        // Request and permission validation.
        $forum = $DB->get_record('forum', array('id' => $discussion->forum), '*', MUST_EXIST);
        list($course, $cm) = get_course_and_cm_from_instance($forum, 'forum');

        $context = context_module::instance($cm->id);
        self::validate_context($context);

        if (!forum_user_can_post($forum, $discussion, $USER, $cm, $course, $context)) {
            throw new moodle_exception('nopostforum', 'forum');
        }

        $thresholdwarning = forum_check_throttling($forum, $cm);
        forum_check_blocking_threshold($thresholdwarning);

        // Create the post.
        $post = new stdClass();
        $post->discussion = $discussion->id;
        $post->parent = $parent->id;
        $post->subject = $params['subject'];
        $post->message = $params['message'];
        $post->messageformat = FORMAT_HTML;   // Force formatting for now.
        $post->messagetrust = trusttext_trusted($context);
        $post->itemid = 0;

        if ($postid = forum_add_new_post($post, null)) {

            $post->id = $postid;

            // Trigger events and completion.
            $params = array(
                'context' => $context,
                'objectid' => $post->id,
                'other' => array(
                    'discussionid' => $discussion->id,
                    'forumid' => $forum->id,
                    'forumtype' => $forum->type,
                )
            );
            $event = \mod_forum\event\post_created::create($params);
            $event->add_record_snapshot('forum_posts', $post);
            $event->add_record_snapshot('forum_discussions', $discussion);
            $event->trigger();

            // Update completion state.
            $completion = new completion_info($course);
            if ($completion->is_enabled($cm) &&
                    ($forum->completionreplies || $forum->completionposts)) {
                $completion->update_state($cm, COMPLETION_COMPLETE);
            }

            $settings = new stdClass();
            $settings->discussionsubscribe = $options['discussionsubscribe'];
//.........这里部分代码省略.........