Thinkphp dwz 三级联动下拉菜单

<h2 class="contentTitle">下拉菜单</h2>

<div class="pageContent" layoutH="56">
<select class="combox" name="province" ref="w_combox_city" refUrl="__URL__/returnCity/cityId/{value}">
<option value="all">所有省市</option>
<option value="bj">北京</option>
<option value="sh">上海</option>
</select>
<select class="combox" name="city" id="w_combox_city" ref="w_combox_area" refUrl="__URL__/returnArea/areaId/{value}">
<option value="all">所有城市</option>
</select>
<select class="combox" name="area" id="w_combox_area">
<option value="all">所有区县</option>
</select>
</div>

<?php
// 三级联动下拉菜单
class ComBoxAction extends CommonAction {

public function returnCity(){
$cityId = $_REQUEST['cityId'];
if($cityId=='sh'){
$arrCity = array(array('all','所有城市'),array('sh','上海市'));
}else if($cityId=='bj'){
$arrCity = array(array('all','所有城市'),array('bj','北京市'));
}else{
$arrCity = array(array('all','所有城市'));
}
echo json_encode($arrCity);
}

public function returnArea(){
$areaId = $_REQUEST['areaId'];
if($areaId=='sh'){
$arrArea = array(array('1','上海城市1'),array('2','上海城市2'));
}else if($areaId=='bj'){
$arrArea = array(array('3','北京城市3'),array('bj','北京城市4'));
}else{
$arrArea = array(array('all','所有城市'));
}

echo json_encode($arrArea);
}

}
?>