php下载文件函数

/*
@desc：php下载文件函数，支持限速
@param name 待下载文件名
@param rate 速度，单位kb
*/
function download($file,$rate=false){
set_time_limit(0);
$content = file_get_contents($file);
$filesize = strlen($content);
header ('Content-Length: '.$filesize);
header ('Content-type: application/file');
header ("Content-Disposition: attachment; filename=".basename($file));
if($rate){
    ob_start();
    $fr=fopen($file,"rb");
    while (!feof($fr)){
        $data = fread($fr,round($rate*1024));
        echo $data;
        ob_flush();
        flush();
        sleep(1);
    }
    if($fr){
        fclose($fr);
    }
}else{
    readfile($file);
}
}

download('2018.rar',128);