Javascript 使用一个php函数返回多个json对象

我试图填充两个下拉菜单，它们的值与另一个菜单的值相关。我总共有3个下拉列表。一个用于选择班级，另两个用于选择所选班级的科目和考试。 我可以填充一个下拉菜单（例如：选择主题）。但是我怎样才能同时填充这两个呢。我的代码如下：

  <table>
       <tr>
          <td> select class</td>
       </tr>
       <tr>
          <td> select subject</td>
       </tr>
         <tr>
          <td> select exam</td>
       </tr>
       <tr>
       <td><select class="form-control m-bot15" name="class_id" value='' onchange="myFunction(this)"  style="float:left;" id="carId">
            <option value="">select a class</option>
             <option value="1">One</option>
             <option value="2">Two</option>
             <option value="3">Three</option>
            </select></td>
         </tr>
         <tr>
         <td><select class="form-control m-bot15" name="subject_id" value='' style="float:left;" id="emptyDropdown">
            <option value="">select a subject</option>
            </select></td>
          <tr>
         </tr>
         <td><select class="form-control m-bot15" name="exam_id" value='' style="float:left;" id="emptyDropdown2">
            <option value="">select a subject</option>
            </select></td>
          </tr>
         </table>

这个很好用。我在下拉列表中找到了主题列表。但我想再传递一个类似这样的json对象

     public function newdrp(){
        $classId = $this->input->post('carId');
        $subjects = $this->subject_model->Subjectbyclassid($classId);
        $exams = $this->exam_model->Exambyclassid($classId);
        echo json_encode(array($subjects,$exams));
  }

这是我的控制台预览

    [[{"subject_id":"1","name":"Physics","class_id":"1","teacher_id":null},{"subject_id":"2","name":"Chemistry","class_id":"1","teacher_id":null},{"subject_id":"3","name":"Mathematics","class_id":"1","teacher_id":null}],[{"exam_id":"22","name":"BW9","date":"03\/10\/16","class_id":"1","comment":""},{"exam_id":"26","name":"BW10","date":"17\/10\/16","class_id":"1","comment":""},{"exam_id":"30","name":"BW11","date":"31\/10\/16","class_id":"1","comment":""},{"exam_id":"34","name":"BW12","date":"14\/11\/16","class_id":"1","comment":""},{"exam_id":"40","name":"BW13","date":"28\/11\/16","class_id":"1","comment":""},{"exam_id":"45","name":"BW14","date":"11\/12\/16","class_id":"1","comment":""},{"exam_id":"46","name":"Revision Exam 1","date":"02\/01\/17","class_id":"1","comment":""},{"exam_id":"49","name":"Revision Exam 2","date":"8\/01\/2017","class_id":"1","comment":""},{"exam_id":"51","name":"Revision Exam 3","date":"15\/01\/17","class_id":"1","comment":""},{"exam_id":"55","name":"Revision Exam 4","date":"22\/01\/17","class_id":"1","comment":""},{"exam_id":"57","name":"Revision exam 5","date":"26\/01\/2017","class_id":"1","comment":""},{"exam_id":"59","name":"Revision Exam 6","date":"29\/01\/17","class_id":"1","comment":""}]]

---

我如何在相应的下拉列表中循环显示考试名称。请帮助

您还必须循环第二个数组，

数据

是父数组

success: function(data){
  var examArr = data[1];
  $.each(examArr, function () {
    $('#emptyDropdown2').append("<option value='" + $(this).exam_id + "'>" + $(this).name + "</option>");
  });
 }

成功：函数（数据）{
var examArr=数据[1]；
$.each（examArr，函数（）{
$（'#empthydropdown2'）.append（“+$（this.name+”）；
});
}

很乐意帮忙！

    [[{"subject_id":"1","name":"Physics","class_id":"1","teacher_id":null},{"subject_id":"2","name":"Chemistry","class_id":"1","teacher_id":null},{"subject_id":"3","name":"Mathematics","class_id":"1","teacher_id":null}],[{"exam_id":"22","name":"BW9","date":"03\/10\/16","class_id":"1","comment":""},{"exam_id":"26","name":"BW10","date":"17\/10\/16","class_id":"1","comment":""},{"exam_id":"30","name":"BW11","date":"31\/10\/16","class_id":"1","comment":""},{"exam_id":"34","name":"BW12","date":"14\/11\/16","class_id":"1","comment":""},{"exam_id":"40","name":"BW13","date":"28\/11\/16","class_id":"1","comment":""},{"exam_id":"45","name":"BW14","date":"11\/12\/16","class_id":"1","comment":""},{"exam_id":"46","name":"Revision Exam 1","date":"02\/01\/17","class_id":"1","comment":""},{"exam_id":"49","name":"Revision Exam 2","date":"8\/01\/2017","class_id":"1","comment":""},{"exam_id":"51","name":"Revision Exam 3","date":"15\/01\/17","class_id":"1","comment":""},{"exam_id":"55","name":"Revision Exam 4","date":"22\/01\/17","class_id":"1","comment":""},{"exam_id":"57","name":"Revision exam 5","date":"26\/01\/2017","class_id":"1","comment":""},{"exam_id":"59","name":"Revision Exam 6","date":"29\/01\/17","class_id":"1","comment":""}]]

success: function(data){
  var examArr = data[1];
  $.each(examArr, function () {
    $('#emptyDropdown2').append("<option value='" + $(this).exam_id + "'>" + $(this).name + "</option>");
  });
 }