当从下拉菜单中他的类别和子类别选择的类型应该在下拉菜单中显示

Question

1) when types selected from dropdown his category and subcategory should be shown 
    in dropdown,problem : when we select types in category it is showing all the category 
    and all the subcategory of other types also 
    please solve this problem as soon as possible. 

    inventory_list.php 
    <select name="typ_id" id="typ_id"> 
    <option>Select a Type</option> 
     <?php 
     $get_types = "select * from types"; 
     $run_types = mysql_query($get_types); 
    while ($row_types=mysql_fetch_array($run_types)){ 
      $typ_id= $row_types['typ_id']; 
     $typ_name = $row_types['typ_name']; 
     echo "<option value='$typ_id'>$typ_name</option>";  
     } 
    ?> 

    <select name="cat_id" id="cat_id"> 
    <option>Select a Category</option> 
    <?php 
    $get_category = "SELECT * FROM category "; 
    $run_category = mysql_query($get_category); 
    while ($row_category=mysql_fetch_array($run_category)){ 
     $cat_id= $row_category['cat_id']; 
     $cat_name = $row_category['cat_name']; 
     echo "<option value='$cat_id'>$cat_name</option>";  
     } 
    ?> 
    </select>   

Answer 1

尝试下面的代码

<script> 
function get_category(type_id){ 
     $.ajax({ 
      type: "POST", 
      url: "get_category.php", 
      data: { type_id : type_id } 
     }).done(function(data){ 
      $("#category").html(data); 
     }); 
    } 
</script> 

<select name="typ_id" id="typ_id" onchange="get_category(this)"> 
    <option>Select a Type</option> 
     <?php 
     $get_types = "select * from types"; 
     $run_types = mysql_query($get_types); 
    while ($row_types=mysql_fetch_array($run_types)){ 
      $typ_id= $row_types['typ_id']; 
     $typ_name = $row_types['typ_name']; 
     echo "<option value='$typ_id'>$typ_name</option>";  
     } 
    ?> 

<div id='category'></div> 

get_category.php

<?php 
     $get_category = "SELECT * FROM category where type_id = $_POST['type_id']"; 
     $run_category = mysql_query($get_category); 
     echo '<select name="cat_id" id="cat_id"> 
     <option>Select a Category</option>'; 

     while ($row_category=mysql_fetch_array($run_category)){ 
      $cat_id= $row_category['cat_id']; 
      $cat_name = $row_category['cat_name']; 
      echo "<option value='$cat_id'>$cat_name</option>";  
      } 
    echo '</select>'; 

?>