File download Ajax/PHP

[ak1dnar]

Hi i need to download some files (.pdf/.doc) from web root.
I am using a ajax script to send the file IDs and PHP will process it and it should generate the save as dialog box.

Currently without ajax when i process PHP file i can open the download box to save the file.
example:
http://localhost/website/download.php?fid=1005

but when i am sending the fid (using a onclick event of a Image i am sending the ID to JS func ) through Ajax Script this PHP file will execute in server side. so can't retrieve those headers to the page i am sending the request. is there any way to Open this dialog box. issue is now the PHP fle is executing in server side, i have to call it in client side as i feel.

var xmlHttp;
function GetXmlHttpObject()
{ 
var objXMLHttp=null;
if (window.XMLHttpRequest)
 {
 objXMLHttp=new XMLHttpRequest();
 }
else if (window.ActiveXObject)
 {
 objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP");
 }
return objXMLHttp;
}
function file_down(fid)
{
xmlHttp=GetXmlHttpObject();
    if (xmlHttp==null)
     {
     alert ("Your Browser does not support AJAX, please Update!");
     return;
     } 
var url="download.php?fid="+fid;
url=url+"&zid="+Math.random();
//xmlHttp.onreadystatechange=stateChanged_file_down;  
xmlHttp.open("GET",url,true);
xmlHttp.send(null);
}
function stateChanged_file_down() 
{ 
if (xmlHttp.readyState==4)
{ 
// Can't guess what to do here....
} 
}

[PHP]
<?php
$fid = $_REQUEST['fid'];
require 'dbcon.php';
$sql="SELECT p_man FROM products where p_id = '$fid'";
$result=mysql_query($sql) or die("Error Occured while Searching Records : " . mysql_error());
$row = mysql_fetch_assoc($result);
$file = $row['p_man'];
if($file)
{
header("Content-Type: application/octet-stream");
header("Content-Length: " . filesize($file));
header('Content-Disposition: attachment; filename="'.$file.'"');
readfile($file);
}
?> [/PHP]