类似火车头 根据条件截取代码。。如何实现？

如
 <div class="imgtag w-146 " >
                        <div class="tag_item">
                            <a target="_blank" href="">
                                <img src="picture/mingxingtupian.jpg" title="广告二" alt="广告二" width="146" height="105" style="width:100%;height:100%;">
                            </a>
                        &nbsp;</div>
                    </div>
类似火车头 我设置 截取头 <div class="imgtag w-146 " >  和 截取尾   &nbsp;</div> 的话  就会得到 中间的内容 如何实现的？谢各位大神