Extracting arrays from http.reponseText

I am completely new to this so please bear with me here. My project involves a webpage executing php scripts via an xmlhttprequest which queries a database and returns data to the webpage. This code below is working to a degree in IE7. As I have not yet parsed http.responseText, I am getting all the code in parts.php in the alert. My php script query creates two php arrays, one a single array and a two-dimensional array such as array[][]. My first question is how can I extract these arrays from http.responseText so I can display them. My 2nd is, stepping through the code in tomcat v5.0.28, the script executes the first alert showing http.readyState = 1, but then stops/fails even with the firewall disabled. Looking at the code below, can anyone suggest a possible reason why? Any help appreciated.

RPJD :)

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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" dir="ltr" lang="en">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8">

<script language="JavaScript">

function Parts()

{ 

var url="http://localhost:8080/Databases/parts.php"; 

if(window.XMLHttpRequest)

http = new XMLHttpRequest(); 

else if (window.ActiveXObject)

http  = new ActiveXObject(Microsoft.XMLHTTP); 

http.onreadystatechange = function()

    { 

    alert(http.readyState);

    if(http.readyState == 4)

        {

        alert(http.status);

        if(http.status == 200)

            {

            result = http.responseText;

            alert(result);

            }    

        else    

            {

            // + " " + http.statusText;

            }    

        } 

    }

http.open("GET", url, true); 

http.setRequestHeader("text/xml"); 

http.send(null); 

} 

</script>

</head>

<body>

<FORM name="description" method="POST" action="">

<p>

<INPUT type="BUTTON" value="Parts"  ONCLICK="Parts();">

</p>

<p>
 
</body>

</html>