Dynamic Drop-Down Menu Question

[surf5502]

So I need to create 3 drop downs. each one feeds off the one above it. so the first dropdown is for a department, when you select that I need every class in that department to come up in the next dropdown. when you select a class i need ever professor for that class to appear in the third dropdown. so i had it working for a solid 10 min... now it doesnt work... (ive been programming php forever, but i am an intermediate with ajax so i feel the error somewhere in the javascript?)

 

HTML

<script type="text/javascript" src="../../js/upload.js"></script>
<form action="" method="post" enctype="multipart/form-data">
<?php if (($_POST['title']!="")&&(!validateForm())) echo "<center><b>Form Invalid</b></center>"; ?>
<?php if (isset($error)) echo "<center><b>Error during file upload</b></center>"; ?>
    <table width="550" align="center" cellpadding="0" cellspacing="0">
        <tr><td><b>Department:</b></td><td><select name="dept" onchange="showClass(this.value)">
            <option value="">-- Select Deptartment --</option>
            <?php
                $query = "SELECT * FROM `categ_dept` ORDER BY `name` ASC";
                $result = mysql_query($query);
                $rows = mysql_num_rows($result);
                $i = 0;
                while ($i < $rows){
                    $name = mysql_result($result, $i, "name");
                    $id = mysql_result($result, $i, "id");
                    echo "<option value=\"$id|$name\"";
                    if ($_POST['dept'] == $id)
                        echo " selected";
                    echo ">$name</option>
            ";
                    $i++;
                }
            ?>
        </select></td></tr>
        <tr><td><b>Class:</b><br/><br/></td><td><div id="txtClass"><select name="class" onchange="showProf(this.value)">
        <option value="">-- Select Deptartment First --</option>
        </select></div><br/><br/></td></tr>
        <tr><td colspan="2" style="border:1px solid #CCCCCC; border-bottom:none; text-align:center; padding-top:10px;"><b><i>If your class is not listed please use this box</i></b></td></tr>
        <tr><td style="border-left:1px solid #CCCCCC; padding:10px;"><b>Class Name:</b></td><td style="border-right:1px solid #CCCCCC;"><input type="text" name="class_name" value="<?php echo $_POST['class_name']; ?>" /></td></tr>
        <tr><td style="border-left:1px solid #CCCCCC; padding:10px;"><b>Call Number:</b><br/><i>ex: W3256</i></td><td style="border-right:1px solid #CCCCCC;"><input type="text" name="class_call" value="<?php echo $_POST['class_call']; ?>" /></td></tr>
        <tr><td style="border-left:1px solid #CCCCCC; padding:10px;"><b>Keywords:</b><br/><i>Seperate by spaces</i></td><td style="border-right:1px solid #CCCCCC;" valign="middle"><input type="text" name="class_keywords" value="<?php echo $_POST['class_keywords']; ?>" /></td></tr>
        <tr><td style="border:1px solid #CCCCCC; border-top:none; border-right:none; padding:10px;"><b>Description:</b></td><td style="border:1px solid #CCCCCC; border-top:none; border-left:none;"><textarea name="class_des" rows="4"><?php echo $_POST['class_des']; ?></textarea></td></tr>
        <tr><td><br/><b>Professor:</b><br/><br/></td><td><br/><div id="txtProf"><select name="professor">
        <option value="">-- Select Class First --</option>
        </select></div><br/><br/></td></tr>
        <tr><td colspan="2" style="border:1px solid #CCCCCC; border-bottom:none; text-align:center; padding-top:10px;"><b><i>If your professor is not listed please use this box</i></b></td></tr>
        <tr><td style="border:1px solid #CCCCCC; border-top:none; border-right:none; padding:10px;"><b>Professor Name:</b></td><td style="border:1px solid #CCCCCC; border-top:none; border-left:none;"><input type="text" name="prof_name" value="<?php echo $_POST['prof_name']; ?>" /></td></tr>
        <tr><td colspan="2" align="center" style="padding-top:30px;"><input type="submit" value="Upload" /></td></tr>
    </table>
    </form>

 

JAVASCRIPT - upload.js

var xmlHttp;
var showID = 0;
function showClass(str){ 
xmlHttp=GetXmlHttpObject();
if (xmlHttp==null){
	alert ("Browser does not support HTTP Request");
	return;
}
showID = 1;
var url="../../includes/getDropdown.php";
url=url+"?q="+str;
url=url+"&sid="+showID;
xmlHttp.onreadystatechange=stateChanged;
xmlHttp.open("GET",url,true);
xmlHttp.send(null);
}
function showProf(str){ 
xmlHttp=GetXmlHttpObject();
if (xmlHttp==null){
	alert ("Browser does not support HTTP Request");
	return;
}
showID = 2;
var url="../../getDropdown.php";
url=url+"?q="+str;
url=url+"&sid="+showID;
xmlHttp.onreadystatechange=stateChanged;
xmlHttp.open("GET",url,true);
xmlHttp.send(null);
}
function stateChanged(){
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete"){ 
	if (showID==1){
		document.getElementById("txtClass").innerHTML=xmlHttp.responseText;
	}else{
		document.getElementById("txtProf").innerHTML=xmlHttp.responseText;
	}
} 
}
function GetXmlHttpObject(){
var xmlHttp=null;
try{
	// Firefox, Opera 8.0+, Safari
	xmlHttp=new XMLHttpRequest();
	if (http_request.overrideMimeType) {
		http_request.overrideMimeType('text/html');
	}
}catch (e){
	//Internet Explorer
	try{
		xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
	}catch (e){
		xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
	}
}
return xmlHttp;
}

 

PHP - getDropdown.php

<?php
@session_start();
$q = $_GET['q'];
$sid = $_GET['sid'];
include ("config.php");
mysql_connect($hostaddr,$username,$password);
@mysql_select_db($database) or die("Error: Database not available. Please try again later.");
if ($sid == 1){
// q is a department id
// return classes for that department
echo "<select name=\"class\" onchange=\"showProf(this.value)\">
	";
$dept = explode("|",$q);
$query = "SELECT * FROM `categ_class` WHERE `dept_id`='".$dept[0]."' AND `school_id`='".$_SESSION['school']."' ORDER BY `name` ASC";
$result = mysql_query($query);
$rows = mysql_num_rows($result);
$i = 0;
if ($rows == 0){
	echo "<option value=\"\">No Classes Listed</option>";
}else{
	echo "<option value=\"\">-- Select a Class --</option>
        ";
	while ($i < $rows){
		$name = mysql_result($result, $i, "name");
		$call = mysql_result($result,$i,"call_num");
		$id = mysql_result($result, $i, "id");
		echo "<option value=\"$id\"";
		if ($_POST['class'] == $id)
			echo " selected";
		echo ">$name ($call)</option>
		";
		$i++;
	}
}
echo "</select>";
}else{
// q is a class id
// return professors for that class
echo "<select name=\"professor\">
	";
$query = "SELECT * FROM `categ_prof` WHERE `class_id`='".mysql_real_escape_string($q)."' ORDER BY `name` ASC";
$result = mysql_query($query);
$rows = mysql_num_rows($result);
$i = 0;
if ($rows == 0){
	echo "<option value=\"\">No Professors Listed</option>";
}else{
	echo "<option value=\"\">-- Select a Professor --</option>
        ";
	while ($i < $rows){
		$name = mysql_result($result, $i, "name");
		$id = mysql_result($result, $i, "id");
		echo "<option value=\"$id\"";
		if ($_POST['professor'] == $id)
			echo " selected";
		echo ">$name</option>
		";
		$i++;
	}
}
echo "</select>";

}
?>

 

 

Any help is greatly appreciated (quicker the better, gotta finish this thing this week)...