<?php

$base = "/ftp";

if (!isset($_GET['id'])) {
    exit("Missing identity");
}

$id = preg_replace('/[^a-zA-Z0-9_-]/', '', $_GET['id']);

$file = "$base/$id.backup";

if (!file_exists($file)) {

    echo "
    <script>
        alert('找不到 {$id} 備份檔，請洽網管部。');
        history.back();
    </script>
    ";

    exit;
}
// 取得檔案最後修改時間（FTP upload time = mtime）
$mtime = filemtime($file);
$date = date("Y-m-d", $mtime);

// 新檔名（只含日期）
$downloadName = $id . "_" . $date . ".backup";

// header下載
header("Content-Type: application/octet-stream");
header("Content-Disposition: attachment; filename=\"$downloadName\"");
header("Content-Length: " . filesize($file));

readfile($file);
exit;