克隆选择标记时，无法从下拉列表中获取POST数据

Question

在我使用jquery之前我的视图代码：

<form name="add_book_form" action="Backend/BookManage/save" method="POST">

    <table width="100%" border="0" class="table" id="center" align="center">

         <tr class="author_div_1">
           <td width="5%">&nbsp;</td>
           <td>Author</td>
           <td>
             <select name="author_1" class="form-control">
               <?php
                  foreach ($authorList as $author) 
                  {
                    echo '<option value = "' . $author["id"] . '">' . $author["name"] . ' ' . $author["surname"] .'</option>';
                  }
               ?>
             </select>
          </td>
          <td>
            <div class="btn glyphicon glyphicon-plus btn-sm" id="add_more_author"></div>
          </td>
        </tr>
        <tr>
          <td height="68" colspan="4" align="center">
             <input type="submit" id="submit_0" value="Save" class="btn btn-primary"/>
             <input type="reset" value="Reset" class="btn btn-danger"/>
          </td>
        </tr>
    </table>

</form>

脚本

var count = 1;
var cloned;
 $(document).on("click", "#add_more_author", function() {
    cloneData = $('.author_div_'+count).clone().attr('class','author_div_'+(++count));
    cloneData.find('.form-control').attr('name','author_'+count);
    cloneData.insertAfter('.author_div_'+ (count-1));
    $('.author_count').attr('value',count);
});

点击add_more_author后，我的html源代码如下：

<select name="author_2" class="form-control">
  <option value="1">First Value</option>
  <option value="2">Second Value</option>
  <option value="3">Third value</option>            
</select>

<select name="author_3" class="form-control">
  <option value="1">First Value</option>
  <option value="2">Second Value</option>
  <option value="3">Third value</option>            
</select>

当我点击add_more_author并选择值然后提交它， 在我的控制器上我回显了POST值，First（author_1）就好了，但另一个我无法得到它。

    echo 'AUTHOR 1 ' . $this->input->post('author_1') . '<br>';
    echo 'AUTHOR 2 ' . $this->input->post('author_2');

结果：

AUTHOR 1 1

作者2