Trouble forcing ZIP download from PHP web app - php

Question

This php file is supposed to:
receive a piece of information from a form on a different page
use this information to create an array of file paths to add to a zip file
create a dynamically named zip file using a class that's included.
force the download of the newly created zip file
numbers 1-3 are working flawlessly.
The page even forces the download of a zip file that is correctly named and is the right size, but when I try to open it, it says the file is invalid. I've seen similar problems in searches, but I have yet to find a solution.
If i enter the direct URL for the newly created zip into the browser, the file downloads and opens perfectly. As a matter of fact, my temporary fix was creating a dynamic direct link to the files :/
I should probably mention that this is hosted on the go daddy economy plan.
<?php
error_reporting(0);
include "gavScripts/connect_to_mysql.php";
require_once 'Zipper.php';
// prepare the file paths to add to the zip file and find the job/client name (for naming the zip folder)
if(isset($_POST['jobName']))
{
$clientID = $_POST['jobName'];
$clientSQL = mysql_query("SELECT clientName FROM job_client WHERE clientID = $clientID");
while($clientRow = mysql_fetch_array($clientSQL))
{
$clientName = $clientRow['clientName'];
}
$zipSQL = mysql_query("SELECT filePath FROM job_expense WHERE clientID = $clientID");
While($zipRow = mysql_fetch_array($zipSQL))
{
$filePaths[] = $zipRow['filePath'];
}
}
//create the zip folder and store the requested files
$zipper = new Zipper();
$zipper->add($filePaths);
$zipper->store('invoices/' . $clientName . '_Invoices.zip');
//download the zip
$fileDownload = 'invoices/' . $clientName . '_Invoices.zip';
$fileName = basename($fileDownload);
header("Content-Type: application/zip");
header("Content-Disposition: attachment; filename=" . $fileName . "");
header("Content-Length: " . filesize($fileDownload));
readfile($fileDownload);
?>

Answer 1

You may have trailing whitespace at the end of your script which is breaking your zip file. Is there a \r or \n (or both) after the closing ?>? Try removing the closing ?> which is optional anyway.

Answer 2

Try the following:
header('Pragma: public');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Last-Modified: '.gmdate ('D, d M Y H:i:s', filemtime($fileName)).' GMT');
header('Cache-Control: private',false);
header('Content-Type: application/zip');
header('Content-Disposition: attachment; filename="'.basename($fileName).'"');
header('Content-Transfer-Encoding: binary');
header('Content-Length: '.filesize($fileName));
header('Connection: close');
readfile($fileName);
exit();
Might help.