Problemi Missing File con ZipArchive

[danlupo]

Salve ho questo problema in LocalHost.

Praticamente mi perde (o non crea il file zip)

<?php

class zip {

    public function comprimi($cartella, $files) {

        $error = ""; //error holder
        if (extension_loaded('zip')) {

// Checking ZIP extension is available
            if ((count($files) > 0)) {
                $zip = new ZipArchive(); // Load zip library 
                $zip_name = time() . ".zip"; // Zip name
                if ($zip->open($zip_name, ZIPARCHIVE::CREATE) !== TRUE) {
// Opening zip file to load files
                    $error .= "* Sorry ZIP creation failed at this time";
                } else {

                    foreach ($files as $v) {

                        $zip->addFile($cartella . $v); // Adding files into zip
                    }
                }
                $zip->close();
                if (file_exists($zip_name)) {

                    // push to download the zip
                    header('Content-type: application/zip');
                    header('Content-Disposition: attachment; filename="' . $zip_name . '"');
                    readfile($zip_name);
// remove zip file is exists in temp path
                } else {
                    $error = 'File non  Trovato';
                }
            } else {
                $error .= "* Selezionare almeno un file da comprimere";
            }
        } else {
            $error .= "* Estensione Zip Non Trovata";
        }
        return $error;
    }

}

?>

Il File lo apre perchè ho provato e mi restituisce 1 sul Zip->Open ma sembra non creare il file $zip_name e non capisco dove sia l'errore.

Daniele