/**
 * 限制文件下载速度
 *
 * @param 
 * @arrange (512.笔记) jb51.cc
 **/
// local file that should be send to the client
$local_file = 'test-file.zip';
 
// filename that the user gets as default
$download_file = 'your-download-name.zip';
 
// set the download rate limit (=> 20,5 kb/s)
$download_rate = 20.5;
 
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();
 
    // open file stream
    $file = fopen($local_file,"r");
 
    while (!feof($file)) {
 
        // send the current file part to the browser
        print fread($file,round($download_rate * 1024));
 
        // flush the content to the browser
        flush();
 
        // sleep one second
        sleep(1);
    }
 
    // close file stream
    fclose($file);
 
}
else {
    die('Error: The file '.$local_file.' does not exist!');
}
/***   代码来自编程之家 jb51.cc（jb51.cc）   ***/