如何从引导程序的下拉菜单中获取这两个值

我必须像这个网站一样创建搜索引擎：http://olx.co.id。 它有三个关键字。第一个是按项目搜索，第二个是按城市搜索，第三个是按类别搜索。用户可以使用一个关键字、两个关键字和三个关键字进行搜索。我没有任何想法来做这件事。这是我的代码，但我不确定它是否运行良好。

    <form method="GET" action="category-grid.php">
    <div class="control-group">
    <input type="text" name="search_item_" class="search-field" placeholder="Searching Item ..." />
        <ul class="categories-filter animate-dropdown">
            <li class="dropdown">       
            <a href="#" class="dropdown-toggle"  data-toggle="dropdown" >All Cities</button>
              <ul class="dropdown-menu" role="menu" id="city" >
                <li role="presentation"><a role="menuitem" tabindex="-1" >Jakarta</a></li>
                <li role="presentation"><a role="menuitem" tabindex="-1" >Singapore</a></li>
                <li role="presentation"><a role="menuitem" tabindex="-1" >Beijing</a></li>  
              </ul>                 
            </li>
        </ul>
        <ul class="categories-filter animate-dropdown">
            <li class="dropdown">
            <a class="dropdown-toggle"  data-toggle="dropdown" href="#">All Categories</a>
               <ul class="dropdown-menu" role="menu" id="category">
                  <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Car</a></li>
                <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Motorcycle</a></li>
                <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Property</a></li>
                <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Industry</a></li>
                <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Elektronic & Gadget</a></li>
                <li role="presentation"><a role="menuitem" tabindex="-1" href="#">Sport</a></li>
              </ul>
            </li>
         </ul>
        <a class="search-button" href="<?php echo base_url();?>search" ></a>    
                    </div>
                </form>

的值，或者在用户更改类别值时获取城市值。

<script>
var city; var category; var item=$('search_item').val();
$('#city li').on('click', function(){
   city = $(this).text();
   if(category == "") window.location.assign('<?php echo base_url()?>index.php/searching/'+city);
   else window.location.assign('<?php echo base_url()?>index.php/searching/'+city+'/'+category);
});
$('#category li').on('click',function(){
   $category = $(this).text();
   if(city == "") window.location.assign('<?php echo base_url()?>index.php/searching/'+category);
   else window.location.assign('<?php echo base_url()?>index.php/searching/'+lokasi+'/'+kategori);
});
<script>

感谢您的所有评论和回答