<?php
function downloadFile($filename, $mimetype='application/octet-stream') {
    if (!file_exists($filename)) die('Файл не найден ' . $filename);

    $from=$to=0; $cr=NULL;

    if (isset($_SERVER['HTTP_RANGE'])) {
        $range=substr($_SERVER['HTTP_RANGE'], strpos($_SERVER['HTTP_RANGE'], '=')+1);
        $from=strtok($range, '-');
        $to=strtok('/'); if ($to>0) $to++;
        if ($to) $to-=$from;
        header('HTTP/1.1 206 Partial Content');
        $cr='Content-Range: bytes ' . $from . '-' . (($to)?($to . '/' . $to+1):filesize($filename));
    } else  header('HTTP/1.1 200 Ok');

    $etag=md5($filename);
    $etag=substr($etag, 0, 8) . '-' . substr($etag, 8, 7) . '-' . substr($etag, 15, 8);
    header('ETag: "' . $etag . '"');

    header('Accept-Ranges: bytes');
    header('Content-Length: ' . (filesize($filename)-$to+$from));
    if ($cr) header($cr);

    header('Connection: close');
    header('Content-Type: ' . $mimetype);
    header('Last-Modified: ' . gmdate('r', filemtime($filename)));
    $f=fopen($filename, 'r');
    header('Content-Disposition: attachment; filename="' . basename($filename) . '";');
    if ($from) fseek($f, $from, SEEK_SET);
    if (!isset($to) or empty($to)) {
        $size=filesize($filename)-$from;
    } else {
        $size=$to;
    }

    $downloaded=0;

    while(!feof($f) and !connection_status() and ($downloaded<$size)) {
        echo fread($f, 512000);
        $downloaded+=512000;
        flush();
    }
    fclose($f);
}
downloadFile($_GET['file']);
?>