codeigniter依賴下拉，使用xmlhttp時出現問題

Question

我在項目中使用依賴下拉菜單。我幾次檢查過我的代碼，但仍然出現錯誤。

數據已加載到'類別'下拉菜單。當Iam從「類別」下面的消息中選擇項目時將顯示。未將數據加載到「子類別」中。

「有一個問題，而使用XMLHTTP」

請看看我的代碼

<!-- /.Category --> 
             <div class="form-group"> 
              <label>Product Category</label> 
              <select name="category_id" class="form-control col-sm-5" id="category" onchange="get_category(this.value)"> 
               <option value="">Select Product Category</option> 
               <?php if (!empty($category)): ?> 
                <?php foreach ($category as $v_category) : ?> 
                 <option value="<?php echo $v_category->category_id; ?>" 
                  <?php 
                  if (!empty($product_info)) { 
                   echo $v_category->category_id == $product_category->category_id ? 'selected' : ''; 
                  } 
                  ?> > 
                  <?php echo $v_category->category_name; ?> 
                 </option> 
                <?php endforeach; ?> 
               <?php endif; ?> 
              </select> 
             </div> 

             <!-- /.Sub Category --> 
             <div class="form-group"> 
              <label>Subcategory<span class="required">*</span></label> 
              <select name="subcategory_id" class="form-control col-sm-5" id="subcategory"> 
               <option value="">Product Subcategory</option> 
               <?php if (!empty($subcategory)): ?> 
                <?php foreach ($subcategory as $v_subcategogy) : ?> 
                 <option value="<?php echo $v_subcategogy->subcategory_id; ?>" 
                  <?php 
                  if (!empty($product_info)) { 
                   echo $v_subcategogy->subcategory_id == $product_info->subcategory_id ? 'selected' : ''; 
                  } 
                  ?> > 
                  <?php echo $v_subcategogy->subcategory_name; ?> 
                 </option> 
                <?php endforeach; ?> 
               <?php endif; ?> 
              </select> 
             </div> 

Ajax代碼（我認爲問題的答覆（req.status == 200）部分。）

//********************************************* 
//  Product Category to Subcategory 
//********************************************* 

function get_category(str) { 

    if (str == '') { 
     $("#subcategory").html("<option value=''>Select Subcategory</option>"); 
    } else { 
     $("#subcategory").html("<option value=''>Select Subcategory</option>"); 

     var link = getBaseURL(); 
     var strURL = link + "admin/product/get_subcategory_by_category/" + str; 
     var req = getXMLHTTP(); 
     if (req) { 

      req.onreadystatechange = function() { 
       if (req.readyState == 4) { 
        // only if "OK" 
        if (req.status == 200) { 
         var result = req.responseText; 
         //alert(result); 
         $("#subcategory").html("<option value=''>Select Subcategory</option>"); 
         $("#subcategory").append(result); 
        } else { 
         alert("There was a problem while using XMLHTTP:\n" + req.statusText); 
        } 
       } 
      } 
      req.open("POST", strURL, true); 
      req.send(null); 
     } 
    } 
} 

Answer 1

它會幫助你如果您正在使用CodeIgniter尋找Dependent下拉列表（庫）。

查看它：Dependent dropdown (library)