自动选择下拉菜单

Question

我有一个类别下拉菜单。当用户从下拉列表中选择任何类别，然后会出现第二个下拉列表。它将显示与类别相关的产品列表（通过jQuery ajax）。

当用户单击从产品下拉列表中的任何条目会重定向到同一页面，但与GET查询..

例如：

page.php?category=3&product=6 

当用户在该网页上，如何自动选择类别下拉菜单和产品下拉菜单？

<label>Category</label> 
    <select id="category"> 
     <option value="0">Please select a category</option> 
     <?php 
      $SQL = "SELECT * FROM category"; 
      $query = mysql_query($SQL); 
      while ($cat = mysql_fetch_assoc($query)) { 
       echo "<option value='{$cat['id']}'>{$cat['name']}</option>"; 
      } 
     ?> 
    </select> 
    <select id="product"> </select> 

    $("#category").change(function() { 
     var category = $(this).val(); 
     $('#product').append($("<option></option>").attr("value","0").text("Please Select Product")); 
     $.getJSON(host + "/ajax_select_product.php?categoryid=" + category, function(data) { 
      $.each (data, function (index, element) { 
       $('#product').append($("<option></option>").attr("value",data[index].id).text(data[index].name)); 
      }); 
     }); 
    }); 

​ 
    $("#product").change(function() { 
     var product = $("#product :selected").val() 
     var category = $("#category :selected").val() 
     window.location = "page.php?category=" + category + "?product=" + product; 
    }); 

Answer 1

你可以用下面的方法做到这一点;

<label>Category</label> 
    <select id="category"> 
     <option value="0">Please select a category</option> 
     <?php 
     $currentCategory = 0; 
     $curretProduct =0; 

     if (!empty($_GET['category'])) { 
      $currentCategory = $_GET['category']; 
     } 

     if (!empty($_GET['product'])) { 
      $currentProduct = $_GET['product']; 
     } 
      $SQL = "SELECT * FROM category"; 
      $query = mysql_query($SQL); 
      while ($cat = mysql_fetch_assoc($query)) { 
       if ($cat['id'] == $currentCategory) { 
       echo "<option value='{$cat['id']}' selected=\"selected\">{$cat['name']}</option>"; 
       } else { 
       echo "<option value='{$cat['id']}'>{$cat['name']}</option>"; 
       } 
      } 
     ?> 
    </select> 
    <select id="product"> </select> 
    var currentProduct = "<?php echo $currentProduct; ?>"; 
    $("#category").change(function() { 
     var category = $(this).val(); 
     $('#product').append($("<option></option>").attr("value","0").text("Please Select Product")); 
     $.getJSON(host + "/ajax_select_product.php?categoryid=" + category, function(data) { 
      $.each (data, function (index, element) { 
       if (data[index].id == currentProduct) { 
        $('#product').append($("<option></option>").attr("value",data[index].id).attr("selected", "selected").text(data[index].name)); 
       } else { 
        $('#product').append($("<option></option>").attr("value",data[index].id).text(data[index].name)); 
       } 

      }); 
     }); 
    }); 

​ 
    $("#product").change(function() { 
     var product = $("#product :selected").text() 
     var category = $("#category :selected").text() 
     window.location = "page.php?category=" + category + "?product=" + product; 
    });