PHP 严格标准: 在.lib 文件中，只有变量应该被作为引用传递

我刚学 PHP，如何更改字符串数据？我浏览了很多话题，但是无法解决这个问题，知识不够

PHP 严格标准: 在 /var/www/html/lib/event.lib 的第 309 行只有变量应该被作为引用传递

    function event_conf() {
    global $session_user,$session;
    $event_artikul_ids = get_hash(event_area_list(array('area_id' => $session_user['area_id']),'','artikul_id'),'artikul_id','artikul_id');
    if (!$event_artikul_ids) return '';
    $event_artikul_ids = get_hash(event_artikul_list(array('id' => $event_artikul_ids),sql_pholder(" AND ((kind = 0) OR (kind = ?)) AND !(flags & ?)",$session_user['kind'], EVENT_FLAG_NO_NOTIFY),'id'),'id','id');
    if (!$event_artikul_ids) return '';
//Line 309
    $event = reset(event_list(array('artikul_id' => $event_artikul_ids), ' AND point_id > 0'));
    if (!$event) return '';
    if (event_track_user_list(array('user_id' => $session_user['id'],'event_id' => $event['artikul_id']), sql_pholder(' AND flags & ?', EVENT_TRACK_USERS_FLAG_HIDE))) return '';
    $event_artikul = event_artikul_get($event['artikul_id']);
    $event_point = event_point_get($event['point_id']);
    $event_point_tasks = make_hash(event_point_task_list(array('point_id' => $event['point_id']),' ORDER BY id'));
    if (!$event_point_tasks) return '';
    $event_point_task_user_hash = get_hash(event_point_task_user_list(array('artikul_id' => $event['artikul_id'], 'user_id' => $session_user['id'])),'task_id','value');
    $event_point_task_value_hash = get_hash(event_point_task_user_list(array('artikul_id' => $event['artikul_id']),' GROUP BY 1','task_id,SUM(value) as value'),'task_id','value');

    $params = array();

PHP 严格标准: 在 /var/www/html/tpl/rating.tpl 的第 155 行只有变量应该被作为引用传递

foreach ($rating_stat as $stat_type => $data_list) {
                    //Line 155
                    echo html_rating_div_str(array_slice($data_list, 0, 10), $users_data, " ID=\"$stat_type" . "_all\" style=\"$style_display\"");
                    $style_display = "display: none;"; // Only first div will be visible
                    $data_kind_list = make_hash($data_list, 'kind', true);

严格标准: 在 /var/www/html/user.php 的第 87 行只有变量应该被作为引用传递

            if ($mode == 'personage') {
                $group = htmlspecialchars(strval($_REQUEST['group']));
 //Line 87
                if (!$user_backpack_groups[$group]) $group = reset(array_keys($user_backpack_groups));
                $mode_url .= '&group='.$group;

请帮忙，告诉我如何修复这些错误。PHP 5.4.45