用在服务器上提供下载的php代码，可以指定被下载的文件名，可以动态指定文件内容

// local file that should be send to the client
$local_file = 'test.zip';
// filename that the user gets as default
$download_file = 'your-download-name.zip';
 
if(file_exists($local_file) && is_file($local_file)) {
    // send headers
    header('Cache-control: private');
    header('Content-Type: application/octet-stream'); 
    header('Content-Length: '.filesize($local_file));
    header('Content-Disposition: filename='.$download_file);
 
    // flush content
    flush();
 
    /*
    ** You can also remove the following part and
    ** replace it trough a database command fetching 
    ** the download data
    */
    // open file stream
    $file = fopen($local_file, "rb");
 
    // send the file to the browser
    print fread ($file, filesize($local_file)); 
 
    // close file stream
    fclose($file);}
else {
    die('Error: The file '.$local_file.' does not exist!');
}