ZIP file not being created, but no error gets triggered

Make sure that:

• All files added actually exist (check each file with file_exists() and is_readable() before calling $zip->addFile()).
• When iterating folder, exclude . and ...
• There is at least one file to zip ($zip['numFiles'] > 0).
• Calling $zip->close() returns TRUE.

Sounds like you have a permission issue, either with writing to the zip file, or reading the files it is zipping.

I would use a combination of file_exists, is_readable, and is_writable to figure out which of these is causing the problem.

function zip_dir($source, $target){

    $iterator = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($source, \FilesystemIterator::SKIP_DOTS), \RecursiveIteratorIterator::SELF_FIRST);

    $zip = new \ZipArchive();
    if($zip->open($target, \ZipArchive::CREATE) !== true)
      exit('cannot create zip');

    foreach($iterator as $file){
      if (!file_exists($file)) { die($file.' does not exist'); }
      if (!is_readable($file)) { die($file.' not readable'); }
      $zip->addFile($file);
      print $file . '<br>';
    }


    $zip->close();
    return $target;
}

if (!is_writable(__DIR__)) { die('directory not writable'); }
zip_dir(__DIR__ . '/test/', __DIR__ . '/testarchive.zip');

Two Comments From php.net

If you're adding multiple files to a zip and your $zip->close() call is returning FALSE, ensure that all the files you added actually exist. Apparently $zip->addFile() returns TRUE even if the file doesn't actually exist. It's a good idea to check each file with file_exists() or is_readable() before calling $zip->addFile() on it.

and

Don't forget to check the zip isn't empty, folks - otherwise the zip won't be created at all, and the server will issue no warning!