Codeigniter 获取编辑表单中multiselect的值

我想编辑一个表单，所以当我在编辑表单中时，之前编辑的值应该显示在该字段中，但我没有从mysql中获得所选的值

我的编辑表格

 <select data-placeholder="Select Rank..." class="chosen-select custom_select " multiple="" style="width: '-webkit-fill-available';" id="rank_restriction" name="rank_restriction[]">

                                        <?php 

                                         foreach ($poll['rankname'] as $rank) { ?>
                                            <option value="<?= $rank ?>"><?= $rank ?></option>
                                       <?php } ?>

                                        </select>

<?php
        if (isset($edit['rank_restriction']) && !empty($edit['rank_restriction'])) {
            $rank_restriction = $edit['rank_restriction']; // array format
        } else {
            $rank_restriction = set_value('rank_restriction'); // again in  array format
        }
        ?>
        <select data-placeholder="Select Rank..." class="chosen-select custom_select " 
                multiple="" style="width: '-webkit-fill-available';" id="rank_restriction" 
                name="rank_restriction[]">

            <?php
            foreach ($poll['rankname'] as $rank) {
                $selected = (!empty($rank_restriction) && in_array($rank, $rank_restriction)) ? 'selected' : '';
                ?>

                <option value="<?= $rank ?>" <?php echo $selected ?>><?= $rank ?> 
                </option>
            <?php } ?>

        </select>