General developer forum

By coping extensively form moodle/mod/data/preset.php (rows 500..502)
I wrote the following code:

$basedir = path to the folder with files to zip
$tozip = array of names of files found in $basedir
foreach ($tozip as $key => $filename) {
$tozip[$key] = $basedir . '/' . $tozip[$key];
}
$exportfile = a_path_I_like/a_name_I_like.zip;
file_exists($exportfile) && unlink($exportfile);
$status = zip_files($tozip, $exportfile);

This routine works, but... why do I find inside my zip file only files and not their container folder?
Why do Martin code creates the folder too?
Where am I wrong?
Where is this code different from the code of Martin?
Thank you in advance.