當從下拉菜單中他的類別和子類別選擇的類型應該在下拉菜單中顯示

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

嘗試下面的代碼

<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>'; 

?>