我已经写了两个下拉框的代码。第一个下拉列表包含主类别动态值的列表。当我选择主要类别列表中的任何一个值时,第二个下拉列表应显示相应的子类别值。我怎样才能做到这一点? 这里是我的代码:?onchange使用php动态下拉值
<div class="row">
<div class="col-xs-6 col-sm-6 col-md-4 col-md-offset-1">
<div class="form-group">
Please Choose Your Category
</div>
</div>
<div class="col-xs-6 col-sm-6 col-md-4 col-md-offset-1">
<div class="form-group">
<select class="form-control" name="category_name" onchange="mainInfo(this.value);">
<option value="" selected>Please Select</option>
<option value="Birds">Birds</option>
<option value="Animals">Animals</option>
<option value="Notinlist">Category Not in list</option>
</select>
</div>
</div>
</div>
<div class="row">
<div class="col-xs-6 col-sm-6 col-md-4 col-md-offset-1">
<div class="form-group">
Please Choose Your Sub Category
</div>
</div>
<div class="col-xs-6 col-sm-6 col-md-4 col-md-offset-1">
<div class="form-group">
<select class="form-control" name="album_name">
<option value="" selected>Please Select</option>
<option value="Birds">Sub Birds</option>
<option value="Animals">Sub Animals</option>
<option value="Notinlist">Category Not in list</option>
</select>
</div>
</div>
</div>
PHP代码的主要类别
<?php
$album_category = $_POST['category_name'];
$sql=$conn->prepare("select * from `albums` where album_category=:album_category");
$sql->bindParam(":album_category",$album_category);
$sql->execute();
while ($row = $sql->fetch(PDO::FETCH_ASSOC))
{
echo $row['album_sub_category'];
} >
感谢您的回答。我的categories.json文件如何看起来像?我该怎么做? –