Automatic Filename Generator - Help Me?!

<?php
//Don't allow the script to timeout
set_time_limit(0);

//Get local file path
$file_path = "./randomfile.rar";

//Abort if the file does not exist
if (!file_exists($file_path))
{
    echo "<h1><font color='red'>ERROR LOCATING FILE</font></h1>";
    die;
}

//Get the file size from the file system (database for display only)
$file_size = filesize($file_path);

//The claimed filename (can be whatever you want... should match proper mime type.)
$claimed_filename = "smackthat.mp3";

//Claimed MIME type--reference list of mime types for different files names at: http://www.feedforall.com/mime-types.htm
$claimed_type = "audio/mpeg";

// Set transfer headers in browser
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Cache-Control: public");
header("Content-Description: File Transfer");
header("Content-Type: $claimed_type");
header("Content-Disposition: attachment; filename=\"$claimed_filename\"");
header("Content-Transfer-Encoding: binary");
header("Content-Length: " . $file_size);

//Transfer the file via the script (impossible for user to see true location on server)
$file = @fopen($file_path,"rb"); //Open file in binary mode
if ($file)
{
    while(!feof($file)) {
        print(fread($file, 1024*8)); //Transfer in 8kb chunks
        flush();
        if (connection_status()!=0) { //What to do if client terminates connection
            @fclose($file);
            die();
        }
    }
    @fclose($file); //Close the file at the end
}
?>