<div class="city">
        <div class="cityName">选择城市</div>
        <div class="cityItem">
            {foreach $data_city as $k=>$v}<span {if $v eq $smarty.get.city}class="cityAct"{/if}><a href="?m=Project&a=cluster&act=ShowCluster&city={$v}#lock{$k}">{$v}</a></span>{/foreach}
        </div>
    </div>
      <div class="city">
            <div class="cityName">选择区县</div>
            <div class="cityItem">
                {foreach $data_area as $p}<span {if $p eq $smarty.get.area}class="cityAct"{/if}><a href="?m=Project&a=cluster&act=ShowCluster&city={$cityName}&area={$p}">{$p}</a></span>{/foreach}
            </div>
        </div>

 $district = array(
            array("city" => "济南市", "areaList" => array("历下区", "市中区", "槐荫区", "天桥区", "历城区", "长清区", "章丘区", "济阳区", "莱芜区", "钢城区", "平阴县", "商河县")),
            array("city" => "青岛市", "areaList" => array("市南区", "市北区", "黄岛区", "崂山区", "李沧区", "城阳区", "即墨区", "胶州市", "平度市", "莱西市", "青岛高新技术产业开发区")),
            array("city" => "淄博市", "areaList" => array("淄川区", "张店区", "博山区", "临淄区", "周村区", "桓台县", "高青县", "沂源县")),
            array("city" => "枣庄市", "areaList" => array("市中区", "薛城区", "峄城区", "台儿庄区", "山亭区", "滕州市")),
            array("city" => "东营市", "areaList" => array("东营区", "河口区", "垦利县", "利津县", "广饶县")),
            array("city" => "烟台市", "areaList" => array("芝罘区", "福山区", "牟平区", "莱山区", "蓬莱区", "龙口市", "莱阳市", "莱州市", "招远市", "栖霞市", "海阳市")),
            array("city" => "潍坊市", "areaList" => array("潍城区", "寒亭区", "坊子区", "奎文区", "临朐县", "昌乐县", "青州市", "诸城市", "寿光市", "安丘市", "高密市", "昌邑市")),
            array("city" => "济宁市", "areaList" => array("任城区", "兖州区", "微山县", "鱼台县", "金乡县", "嘉祥县", "汶上县", "泗水县", "梁山县", "曲阜市", "邹城市")),
            array("city" => "泰安市", "areaList" => array("泰山区", "岱岳区", "新泰市", "肥城市", "宁阳县", "东平县")),
            array("city" => "威海市", "areaList" => array("环翠区", "文登区", "荣成市", "乳山市")),
            array("city" => "日照市", "areaList" => array("东港区", "岚山区", "五莲县", "莒县")),
            array("city" => "临沂市", "areaList" => array("兰山区", "罗庄区", "河东区", "郯城县", "兰陵县", "莒南县", "沂水县", "蒙阴县", "平邑县", "费县", "沂南县", "临沭县", "临沂高新技术产业开发区")),
            array("city" => "德州市", "areaList" => array("德城区", "陵城区", "宁津县", "庆云县", "临邑县", "齐河县", "平原县", "夏津县", "武城县", "乐陵市", "禹城市")),
            array("city" => "聊城市", "areaList" => array("东昌府区", "阳谷县 ", "莘县", "茌平区", "东阿县", "冠县", "高唐县", "临清市")),
            array("city" => "滨州市", "areaList" => array("滨城区", "沾化区", "惠民县", "阳信县", "无棣县", "博兴县", "邹平市")),
            array("city" => "菏泽市", "areaList" => array("牡丹区", "定陶区", "曹县", "单县", "成武县", "巨野县", "郓城县", "鄄城县", "东明县", "菏泽经济技术开发区", "菏泽高新技术产业开发区"))
        );
        $citys = filterArrayByCity($district);
        $cityName = get_param('city');
        if ($cityName == "") {
            $cityName = "济南市";
        }
        $areas = filterArrayByKey($district, 'city', $cityName);

function filterArrayByCity($array)
{
    $result = array();
    foreach ($array as $v) {
        $result[] = $v["city"];
    }
    return $result;
}

//筛选数组
function filterArrayByKey($array, $key, $value)
{
    $result = array();
    foreach ($array as $item) {
        if (isset($item[$key]) && $item[$key] == $value) {
            $result[] = $item["areaList"];
        }
    }
    return $result[0];
}

<!-- 城市下拉列表 -->
<select id="citySelect" onchange="loadCounties()">
  <option value="">请选择城市</option>
  <option value="beijing">北京</option>
  <option value="shanghai">上海</option>
  <!-- 其他城市选项 -->
</select>
<!-- 区县下拉列表 -->
<select id="countySelect">
  <option value="">请选择区县</option>
</select>

function loadCounties() {
  var citySelect = document.getElementById("citySelect");
  var countySelect = document.getElementById("countySelect");
  var selectedCity = citySelect.value;
  // 清空区县下拉列表
  countySelect.innerHTML = '<option value="">请选择区县</option>';
  // 根据选择的城市加载对应的区县列表
  if (selectedCity === "beijing") {
    loadBeijingCounties();
  } else if (selectedCity === "shanghai") {
    loadShanghaiCounties();
  }
  // 根据其他城市加载对应的区县列表
}
function loadBeijingCounties() {
  // 向后端发送异步请求，获取北京市的区县列表
  // 在回调函数中处理返回的数据，动态生成区县选项，添加到countySelect中
  // 示例中使用静态数据作为示范
  var counties = ["东城区", "西城区", "朝阳区", "海淀区", "丰台区"];
  for (var i = 0; i < counties.length; i++) {
    var option = document.createElement("option");
    option.text = counties[i];
    option.value = counties[i];
    countySelect.add(option);
  }
}
function loadShanghaiCounties() {
  // 向后端发送异步请求，获取上海市的区县列表
  // 在回调函数中处理返回的数据，动态生成区县选项，添加到countySelect中
  // 示例中使用静态数据作为示范
  var counties = ["黄浦区", "徐汇区", "静安区", "长宁区", "普陀区"];
  for (var i = 0; i < counties.length; i++) {
    var option = document.createElement("option");
    option.text = counties[i];
    option.value = counties[i];
    countySelect.add(option);
  }
}