ZipArchive downloading empty zip files - php

Question

I am attempting to create a zip file that has a simple text file inside. Unfortunatly when I open the zip file, the file is empty, although in the code I have added in a text file.
I have looked for other questions on the topic with no avail and I have tried adding different files such as photos , but the zip is always empty.
How can I succesfully add files to my zip?
Here is the commented code
if($_POST['down']){
ob_clean(); //clean and flush
ob_end_flush();
$zip = new ZipArchive(); //create new zip
$filename = 'images.zip'; //call the zip a name
if($zip->open($filename, ZipArchive::CREATE) == FALSE){ //if zip can't be opened or created, kill the script
die('nozip');
}
$string = 'wef2emfofp32fo2mfomepofm'; // a string
$zip->addFromString('text.txt', $string); //add the string to the zip
$zip->close(); //close zip
header("Content-Disposition: attachment; filename=".basename(str_replace(' ', '_', $filename)));
header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/zip");
header("Content-Description: File Transfer");
header("Content-Length: " . filesize($filename));
//download the zip
}

Answer 1

remove these codes
if($zip->open($filename, ZipArchive::CREATE) == FALSE){ //if zip can't be opened or created, kill the script
die('nozip');
}
and surround everything else with a try catch block. You might find answers in the exception message if that block is not itself the cause.

Answer 2

With this simple code (from php documentaion)
I have created succesfully the zip and the content
<?php
$zip = new ZipArchive;
$res = $zip->open('test.zip', ZipArchive::CREATE);
if ($res === TRUE) {
$zip->addFromString('test.txt', 'file content goes here');
$zip->close();
echo 'ok';
} else {
echo 'failed';
}
?>