/**
 * PHP控制文件下载速度
 *
 * @param 
 * @arrange 网： jb51.cc
 **/
/* set here a limit of downloading rate (e.g. 10.20 Kb/s) */
$download_rate = 10.20;
$download_file = 'download-file.zip';  
$target_file = 'target-file.zip';
if(file_exists($download_file)){
	/* headers */
	header('Last-Modified: '.gmdate('D,d M Y H:i:s').' GMT');
	header('Cache-control: private');
	header('Content-Type: application/octet-stream');
	header('Content-Length: '.filesize($download_file));
	header('Content-Disposition: filename='.$target_file);
	/* flush content */
	flush();
	/* open file */
	$fh = @fopen($download_file,'r');
	while(!feof($fh)){
		/* send only current part of the file to browser */
		print fread($fh,round($download_rate * 1024));
		/* flush the content to the browser */
		flush();
		/* sleep for 1 sec */
		sleep(1);
	}
	/* close file */
	@fclose($fh);
}else{
	die('Fatal error: the '.$download_file.' file does not exist!');
}
/***   来自编程之家 jb51.cc（jb51.cc）   ***/