$files→zip() with files array

[kater]

Hi,

Failing to generate a zip from files array (rel. or abs., file-field from user template).
No Errors.
Generating from directory ($dir, inside assets) works just fine.
Could it be a permission issue?

https://processwire.com/api/ref/wire-file-tools/zip/

Thanks!

// User files
$invoices = [];
$regUsers = $pages->find('template=user, check_access=0, include=hidden');
foreach ($regUsers as $regUser) {
    if ($regUser->user_invoices->last()) {
        $invoices[] = $regUser->user_invoices->last()->url;
    }
}

// ZIP Archiv
$dir = wire('config')->paths->assets . "pdfs/"; //for testing
$filename = "Invoices_" . date('d-m-y_H-m-s') . ".zip";
$zip = wire('config')->paths->assets . "pdfs-invoices/" . $filename;
$result = wire('files')->zip(
    $zip,
    $invoices,
    array(
        'overwrite' => 'true',
        'allowHidden' => 'true'
    )
);