What did i do wrong with my downloader code? [PHP]

I am trying to randomly download some files and I apologize because I posted it earlier but can someone explain what I am doing wrong in detail? I can not seem to debug it as I know minimal php :/

<?php 
$rootPath = realpath('./uploads');
//make zip file
$zip = new ZipArchive();
$zip->open('file.zip', ZipArchive::CREATE | ZipArchive::OVERWRITE);
$nfiles = glob($rootPath.'*.{aiff}', GLOB_BRACE);     
$files = array_rand($nfiles, 20);
foreach($files as $file)  {
    $pathtofile = $nfiles[$file];
 if (!$file->isDir())
{
    // Get path for current file
    $filePath = $pathtofile->getRealPath();
    $relativePath = str_replace($rootPath, "", $file);
    // Add file to zip
    $zip->addFile($filePath, $relativePath);
}
}
 //-------------------------------------------//
 $zip->close();
 header('Content-Type: application/zip');
 header('Content-disposition: attachment; filename='.'generatedsounds.zip');
 header('Content-Length: ' . filesize('file.zip'));
 readfile('file.zip');
  if(file_exists('file.zip'))
{
  unlink('file.zip');
}
?>