我正在使用以下代码,但我不知道如何更改/加载子选择框中的内容,具体取决于父选择框选项
<div class="middle_row row_white search_row">
<div class="container">
<form action="#" class="search_form advsearch_hide clearfix">
<div class="row field_select">
<label class="label_title">Select Product:</label>
<select name="car_maker" class="select_styled">
<option value="0" class="default">- SELECT -</option>
<option value="1">Automatic Filling Lines</option>
<option value="2">Packaging Machines for Food industries & Bakaries</option>
<option value="3">Automatic Vertical Packaging Machines</option>
<option value="4">Vacuum Machines</option>
<option value="5">Gluing Machines</option>
<option value="6">Automatic Shrink Wrapping</option>
<option value="7">Automatic Cup Filling & Sealing Machines</option>
<option value="8">Banding Machines</option>
<option value="9">Packaging Materials</option>
</select>
</div>
<div class="row field_select">
<label class="label_title">Select Category:</label>
<select class="select_styled" name="car_model">
<option value="0" class="default">- SELECT -</option>
<option value="1">Category1</option>
<option value="2">Category2</option>
<option value="3">Category3</option>
<option value="4">Category4</option>
<option value="5">Category5</option>
<option value="6">Category6</option>
</select>
</div>
<div class="row field_select">
<label class="label_title">Select Model:</label>
<select class="select_styled" name="car_year">
<option value="0" class="default">- SELECT -</option>
<option value="1">Model1</option>
<option value="2">Model2</option>
<option value="3">Model3</option>
<option value="4">Model4</option>
<option value="5">Model5</option>
<option value="6">Model6</option>
</select>
</div>
而且我不知道如何根据父选择框选项更改/加载子选择框中的内容?请你帮助我好吗...