Download AJAX chained select

Licensing

This script is distributed under the LGPL open source license.
Commercial licenses are also available. Some of these licenses also includes personal e-mail support for up to 1 year.

PHP

This script requires PHP. You can also other server side languages if you rewrite the code for getCities.php(See below)

Put this into your <HEAD> section

<style type="text/css">
body{
	background-repeat:no-repeat;
	font-family: Trebuchet MS, Lucida Sans Unicode, Arial, sans-serif;
	height:100%;
	background-color: #FFF;
	margin:0px;
	padding:0px;
}
select{
	width:150px;
}
</style>
<script type="text/javascript" src="ajax.js"></script>
<script type="text/javascript">
/************************************************************************************************************
Ajax chained select
Copyright (C) 2006  DTHMLGoodies.com, Alf Magne Kalleland

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

Dhtmlgoodies.com., hereby disclaims all copyright interest in this script
written by Alf Magne Kalleland.

Alf Magne Kalleland, 2006
Owner of DHTMLgoodies.com


************************************************************************************************************/	
var ajax = new Array();

function getCityList(sel)
{
	var countryCode = sel.options[sel.selectedIndex].value;
	document.getElementById('dhtmlgoodies_city').options.length = 0;	// Empty city select box
	if(countryCode.length>0){
		var index = ajax.length;
		ajax[index] = new sack();
		
		ajax[index].requestFile = 'getCities.php?countryCode='+countryCode;	// Specifying which file to get
		ajax[index].onCompletion = function(){ createCities(index) };	// Specify function that will be executed after file has been found
		ajax[index].runAJAX();		// Execute AJAX function
	}
}

function createCities(index)
{
	var obj = document.getElementById('dhtmlgoodies_city');
	eval(ajax[index].response);	// Executing the response from Ajax as Javascript code	
}


function getSubCategoryList(sel)
{
	var category = sel.options[sel.selectedIndex].value;
	document.getElementById('dhtmlgoodies_subcategory').options.length = 0;	// Empty city select box
	if(category.length>0){
		var index = ajax.length;
		ajax[index] = new sack();
		
		ajax[index].requestFile = 'getSubCategories.php?category='+category;	// Specifying which file to get
		ajax[index].onCompletion = function(){ createSubCategories(index) };	// Specify function that will be executed after file has been found
		ajax[index].runAJAX();		// Execute AJAX function
	}
}
function createSubCategories(index)
{
	var obj = document.getElementById('dhtmlgoodies_subcategory');
	eval(ajax[index].response);	// Executing the response from Ajax as Javascript code	
}		
</script>

Put this into your <BODY> section

<form action="" method="post">
<table>
	<tr>
		<td>Country: </td>
		<td><select id="dhtmlgoodies_country" name="dhtmlgoodies_country" onchange="getCityList(this)">
			<option value="">Select a country</option>
			<option value="dk">Denmark</option>
			<option value="no">Norway</option>
			<option value="us">US</option>
		</select>
		</td>
	</tr>
	<tr>
		<td>City: </td>
		<td><select id="dhtmlgoodies_city" name="dhtmlgoodies_city">
		
		</select>
		</td>
	</tr>
	<tr>
		<td colspan="2"><b>Second example</b></td>
	</tr>
	<tr>
		<td>Category: </td>
		<td><select id="dhtmlgoodies_category" name="dhtmlgoodies_category" onchange="getSubCategoryList(this)">
			<option value="">Select a category</option>
			<option value="1">Cars</option>
			<option value="2">Boats</option>
			<option value="3">Airplanes</option>
		</select>
		</td>
	</tr>
	<tr>
		<td>Sub category: </td>
		<td><select id="dhtmlgoodies_subcategory" name="dhtmlgoodies_subcategory">
		
		</select>
		</td>
	</tr>
</table>
</form>

Download Javascript file

I have used the Simple Ajax Code Kit library(SACK) for this script. I have made a copy available for download here.

Put ajax.js in a subfolder called "js" or change the path to the file in the code above(i.e. <script type="text/javascript" src="js/ajax.js"></script>)

Configuration

This script works like this:

Someone select a country from the select box. This triggers the function getCityList()
Ajax executes the file getCities.php to get a list of cities from the selected country
The script executes the response from Ajax, i.e. creates a list of cities in the second select box

getCities.php

Ajax sends a request to the file getCities.php which returns a list of cities. A server side script like this will usually return data from a database. However, I have in this demo used static data to make things simple.

Here's the content of getCities.php:

<?php

if(isset($_GET['countryCode'])){

  switch($_GET['countryCode']){

    case "no":
      echo "obj.options[obj.options.length] = new Option('Bergen','1');\n";
      echo "obj.options[obj.options.length] = new Option('Haugesund','2');\n";
      echo "obj.options[obj.options.length] = new Option('Oslo','3');\n";
      echo "obj.options[obj.options.length] = new Option('Stavanger','4');\n";

      break;
    case "dk":

      echo "obj.options[obj.options.length] = new Option('Aalborg','11');\n";
      echo "obj.options[obj.options.length] = new Option('Copenhagen','12');\n";
      echo "obj.options[obj.options.length] = new Option('Odense','13');\n";

      break;
    case "us":

      echo "obj.options[obj.options.length] = new Option('Atlanta','21');\n";
      echo "obj.options[obj.options.length] = new Option('Chicago','22');\n";
      echo "obj.options[obj.options.length] = new Option('Denver','23');\n";
      echo "obj.options[obj.options.length] = new Option('Los Angeles','24');\n";
      echo "obj.options[obj.options.length] = new Option('New York','25');\n";
      echo "obj.options[obj.options.length] = new Option('San Fransisco','26');\n";
      echo "obj.options[obj.options.length] = new Option('Seattle','27');\n";

      break;
  }
}

?>