无法查看使用php的ZipArchive函数创建的Zip（但有内存）内的文件

<?php
       $error = "";
       $file_folder = "temp/";
        // folder to load files
 if (extension_loaded('zip')) {
    // Checking ZIP extension is available
    $zip = new ZipArchive();
    // Load zip library
    $zip_name = "images_".date("d-m-Y") . ".zip";
    // Zip name
    if ($zip -> open($zip_name, ZIPARCHIVE::CREATE) !== TRUE) {
        // Opening zip file to load files
        $error .= "* Sorry ZIP creation failed at this time";
    }
    $iterator = new RecursiveIteratorIterator(new RecursiveDirectoryIterator("../uploads/"));
    $files = iterator_to_array($iterator, true);

    foreach ($iterator as $file) {
        $zip -> addFile($file_folder . $file);
        // Adding files into zip
    }
    print_r($zip);
    //echo $zip_name;
    if (file_exists($file_folder.$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
        unlink($zip_name);
    } else {
        echo "error";
    }

    $zip -> close();
//} else
//  $error .= "* Please select file to zip ";
 } else
$error .= "* You dont have ZIP extension";

?>
<?php
       $error = "";
       $file_folder =