I needed to read through a log file looking for certain entries backwards (newest entries first). Perl has a File::ReadBackwards module that does exactly this:

use File::ReadBackwards;

my $file = "/var/log/message";
my $fh   = File::ReadBackwards->new($file) or die "can't read $file";

while (my $line = $fh->readline()) {
    print $line;
}

If you want to a simple way to serve a file for download in PHP you can use this function:

function serve_file($filepath) {
    $filename = basename($filepath);

    if (headers_sent()) {
        die("Cannot output file because output already started");
    }

    $mime_type = mime_content_type($filepath);
    header("Content-type: $mime_type");
    header("Content-Disposition: attachment; filename=\"$filename\"");

    readfile($filepath);

    exit(0);
}