如何使用ListBox通过GET方法发送多个变量

I would like to make a ListBox that can send 2 variables (called category and order) to shopping.php by GET method with single click on ListBox.

So that shopping.php can use the variables $_GET['category'] and $_GET['order']

How can I do that?

<form method="GET">
<select name="XXX" onchange="javascript: submit()">
  <option value="" selected="">Please select here</option>
  <option value="shopping.php?category=Dictionary&order=bookTitle">Order by book title</option>
  <option value="shopping.php?category=Dictionary&order=price">Order by price</option>
</select>
</form>

Change your code to

<form method="GET">
<input type="hidden" name="category" value="Dictionary">
<select name="order" onchange="javascript: submit()">
  <option value="" selected="">Please select here</option>
  <option value="bookTitle">Order by book title</option>
  <option value="price">Order by price</option>
</select>
</form>