Laravel response macro for streamed responses with seeking support

streamed.php

<?php

Response::macro('streamed', function($type, $size, $name, $callback) {
    $start = 0;
    $length = $size;
    $status = 200;

    $headers = [
        'Content-Type' => $type,
        'Content-Length' => $size,
        'Accept-Ranges' => 'bytes'
    ];

    if (false !== $range = Request::server('HTTP_RANGE', false)) {
        list($param, $range) = explode('=', $range);

        if (strtolower(trim($param)) !== 'bytes') {
            header('HTTP/1.1 400 Invalid Request');
            exit;
        }

        list($from, $to) = explode('-', $range);

        if ($from === '') {
            $end = $size - 1;
            $start = $end - intval($from);
        } elseif ($to === '') {
            $start = intval($from);
            $end = $size - 1;
        } else {
            $start = intval($from);
            $end = intval($to);
        }

        $length = $end - $start + 1;

        $status = 206;
        $headers['Content-Range'] = sprintf('bytes %d-%d/%d', $start, $end, $size);
    }

    return Response::stream(function() use ($start, $length, $callback) {
        call_user_func($callback, $start, $length);
    }, $status, $headers);
});