我正在尝试使用Codeigniter中的Mysql数据库开发4级动态菜单。主菜单和子菜单正常显示，但第三级和第四级没有显示。谁能帮我吗？

<?php 
foreach($main_menu as $mmenu): ?>
    <?php if($mmenu->main_id != $mmenu->item_main_id): ?>
        <li>
            <a href='<?php echo base_url(); ?><?php echo $mmenu->m_name; ?>'><?php echo $mmenu->m_name; ?></a>
        </li>
    <?php else: ?>
        <li class='has-sub'><a href='#'><?php echo $mmenu->m_name; ?></a>
            <ul>
            <?php foreach($sub_menu as $smenu): ?>
                <?php if($mmenu->main_id == $smenu->m_id): ?>   
                    <li class='has-sub'>
                        <a href='<?php echo base_url(); ?><?php echo $smenu->m_item_name; ?>'><?php echo $smenu->m_item_name; ?></a>
                        <ul>
                            <?php foreach($sub_submenu as $ssmenu): ?>
                                <?php if($smenu->sub_id != $ssmenu->m_item_id): ?> 
                                <?php else: ?>
                                    <li class='has-sub'><a href='<?php echo base_url(); ?><?php echo $ssmenu->m_item_sub_name; ?>'><?php echo $ssmenu->m_item_sub_name; ?></a>
                                        <ul>
                                            <?php foreach($sub_menu_second as $sssmenu): ?>
                                                <?php if($ssmenu->submenu_id == $sssmenu->m_item_sub_id): ?>
                                                    <li class="has-sub">
                                                        <a class="pl-5" href=''><?php echo $sssmenu->m_item_sub_item_name; ?></a>           
                                                    </li>
                                                <?php elseif(empty($sssmenu->m_item_sub_id)): ?>
                                                    <li>
                                                        <a class="pl-5" href=''><?php echo $sssmenu->m_item_sub_item_name; ?></a>
                                                    </li>
                                                <?php endif; ?> 
                                            <?php endforeach; ?>
                                        </ul>
                                    </li>
                                <?php endif; ?> 
                            <?php endforeach; ?>                                
                        </ul>
                    </li>
                <?php else;  ?> 
                    <li><a href='<?php echo base_url(); ?><?php echo $smenu->m_item_name; ?>'><?php echo $smenu->m_item_name; ?></a></li>
                <?php endif; ?> 

            <?php endforeach; ?>
            </ul>
        </li>
    <?php endif ?>
<?php endforeach; ?>