<select class="data" multiple=""multiple"" name="data[]"> <option selected="">11111</option> <option selected="">22222</option> <option selected="">33333</option> <option selected="">44444</option> <option selected="">55555</option> </select>
select未选择任何选项时提交表单,后台不会接受到该数据 $_POST['data']=""或$_POST['data']=null;而是不存在$data,即isset($_POST['data'])=false。html
为解决这个问题,当未选时让后台接收到一个空值,可加入一个空选项<option selected=""></option>code
<select class="data" multiple=""multiple"" name="data[]"> <option selected="" style="display:none"></option> <option selected="">11111</option> <option selected="">22222</option> <option selected="">33333</option> <option selected="">44444</option> <option selected="">55555</option> </select>