force download of documents and audio

<?php

$filename = $_GET['file'];

// NOTE: YOU SHOULD HARDCODE IN A FILE LOCATION OR RESTRICT DIRECTORIES SO THAT THE ACCESS IS RESTRICTED
//FOR EXAMPLE
//if(substr($filename, 0,5)!='mydir') { exit; } //restrict download access to a link beginning with mydir only
//the link would then be something like http://mysite.com/force-download.php?file=mydir/myFile.jpg

//http://elouai.com/force-download.php
//EXAMPLE LINK http://mysite.com/force-download.php?file=bookmarks/apple-heart.jpg
// required for IE, otherwise Content-disposition is ignored
if(ini_get('zlib.output_compression'))
  ini_set('zlib.output_compression', 'Off');

// addition by Jorg Weske
$file_extension = strtolower(substr(strrchr($filename,"."),1));

if( $filename == "" )
{
  echo "<html><body OnLoad=\"javascript: alert('Sorry, file not found...');history.back();\" bgcolor=\"#F0F0F0\"></body></html>";
  exit;
} elseif ( ! file_exists( $filename ) )
{
  echo "<html><body OnLoad=\"javascript: alert('Sorry, file not found...');history.back();\" bgcolor=\"#F0F0F0\"></body></html>";
  exit;
};
switch( $file_extension )
{
  case "pdf": $ctype="application/pdf"; break;
  case "exe": $ctype="application/octet-stream"; break;
  case "zip": $ctype="application/zip"; break;
  case "doc": $ctype="application/msword"; break;
  case "xls": $ctype="application/vnd.ms-excel"; break;
  case "ppt": $ctype="application/vnd.ms-powerpoint"; break;
  case "gif": $ctype="image/gif"; break;
  case "png": $ctype="image/png"; break;
  case "jpeg":
  case "jpg": $ctype="image/jpg"; break;
  default: $ctype="application/force-download";
}
header("Pragma: public"); // required
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Cache-Control: private",false); // required for certain browsers
header("Content-Type: $ctype");
// change, added quotes to allow spaces in filenames, by Rajkumar Singh
header("Content-Disposition: attachment; filename=\"".basename($filename)."\";" );
header("Content-Transfer-Encoding: binary");
header("Content-Length: ".filesize($filename));
readfile("$filename");
exit();

?>