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I started working from this example http://www.w3schools.com/ajax/ajax_database.asp. I want create dynamic drop down menus. I have hit a wall now and am not sure what to do. Could someone have a look at my code and tell me where I need to make adjustments. Basically nothing is happening at all right now.

 

menutest.php

<?php 
session_start();
include("../db_connect.php");
$query = "SELECT * FROM trip ORDER BY year";
query_db($query);
?>

<html>
<head>
<script src="select.js"></script>
</head>
<body>

<form name="search" method="get"> 

<?php
$query = "SELECT * FROM trip ORDER BY year";
query_db($query);
?>
<select name="year" onChange="updateMenu(this.value,day)">
<option>Year</option>
<?php
while ($row = mysql_fetch_array($result))
{
extract($row); ?>
<option value="<?php echo $year; ?>"><?php echo $year; ?></option>
<?php } ?>
</select>  


<select disabled="disabled" id="day" name="day" onChange="updateMenu(this.value,event)">
<option>Day       </option>
</select><br />

<select disabled="disabled" id="name" name="event" onChange="updateMenu(this.value,submit)">
<option>Event     </option>
</select><br />

</form>


</body>
</html>

 

select.js

var xmlHttp

function updateMenu(str,menu)
{ 
xmlHttp=GetXmlHttpObject()
if (xmlHttp==null)
{
alert ("Browser does not support HTTP Request")
return
}
var url="getmenu.php"
url=url+"?q="+str+"&m="+menu
url=url+"&sid="+Math.random()
xmlHttp.onreadystatechange=stateChanged 
xmlHttp.open("GET",url,true)
xmlHttp.send(null)
}

function stateChanged() 
{ 
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
{ 
	if (menu=="day")
{
 document.getElementById("day").innerHTML=xmlHttp.responseText 
}
 if (menu=="event")
{
 document.getElementById("name").innerHTML=xmlHttp.responseText 
}

} 
}

function GetXmlHttpObject()
{
var xmlHttp=null;
try
{
// Firefox, Opera 8.0+, Safari
xmlHttp=new XMLHttpRequest();
}
catch (e)
{
//Internet Explorer
try
  {
  xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
  }
catch (e)
  {
  xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
}
return xmlHttp;
}

getmenu.php

<?php
session_start();
include("../db_connect.php");

$q=$_GET["q"];
$m=$_GET["m"];



if ($m == "day")
{

$query = "SELECT * FROM `$q` ORDER BY id";
query_db($query);

echo "<select id='day' name='day'>"
while ($row = mysql_fetch_array($result))
{
extract($row); 
$timestamp = strtotime($edate);
$showdate = date('F j', $timestamp);
echo "<option value='$id'>Day $id - $showdate</option>";

}
echo "</select><br />";
}

if ($m == "event")
{
$query = "SELECT * FROM event WHERE day = $q ORDER BY day";
query_db($query);

echo "<select id='even' name='event'>";
while ($row = mysql_fetch_array($result))
{
extract($row); 
$length = strlen($event);
$abvevent = substr($event,0,26);
echo "<option value='$eventid'> $abvevent";
if ($length >= 26) {echo "...";} 
echo "</option>";
} 
echo "</select><br />";

?>

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Well  in menutest.php...

 

<select name="year" onChange="updateMenu(this.value,day)">

 

the updateMenu() function takes the two values then in select.js they are turned into $_GET variabes and sent to getmenu.php...

 

var url="getmenu.php"
url=url+"?q="+str+"&m="+menu

 

 

then in get menu.php

 

$q=$_GET["q"];
$m=$_GET["m"];

 

the naming of the q came from the example at w3schools.com that I used. and in my DB I have colums in a table with years as names for example `2007`

 

I hope that all makes sense. I'm not even sure if what i did was right, thats why I put this up here.

 

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I noticed a little something. You have the id attribute in the select and your updating the innerHTML inside the the select. This is not right.

 

To save you some pain concerning IE6 do NOT try to update the html inside the select box IE has some issues with it.

look at your php ajax query it will echo something like:

<select id="day">
    <option></option>
    <option></option>
    <option></option>
</select>

 

and with the following line inside the function stateChanged()

document.getElementById("day").innerHTML

 

you will update the html inside your select so your updated page will look like:

<select id="day">
<select id="day">
    <option></option>
    <option></option>
    <option></option>
</select>
</select>

 

hmmm that can't be good so try placing each select box inside a div instead like this

<div id="day">
<select>
    <option></option>
    <option></option>
    <option></option>
</select>
</div>

that should solve one thing now something else i saw

 

inside your functionstateChanged() is saw this

if(menu=="day")

however your variable menu only exists inside the function updateMenu() and will cease to exist outside that function declare it outside that function

var menu;
function stateChanged(){
}

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