<?php 
// grab the requested file's name
$file_name = $_GET['file'];

// make sure it's a file before doing anything!
if(is_file($file_name)) {

  /*
    Do any processing you'd like here:
    1.  Increment a counter
    2.  Do something with the DB
    3.  Check user permissions
    4.  Anything you want!
  */

  // required for IE
  if(ini_get('zlib.output_compression')) { ini_set('zlib.output_compression', 'Off');  }

  // get the file mime type using the file extension
  switch(strtolower(substr(strrchr($file_name, '.'), 1))) {
    case 'pdf': $mime = 'application/pdf'; break;
    case 'zip': $mime = 'application/zip'; break;
    case 'jpeg':
    case 'jpg': $mime = 'image/jpg'; break;
    default: $mime = 'application/force-download';
  }
  header('Pragma: public');   // required
  header('Expires: 0');    // no cache
  header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
  header('Last-Modified: '.gmdate ('D, d M Y H:i:s', filemtime ($file_name)).' GMT');
  header('Cache-Control: private',false);
  header('Content-Type: '.$mime);
  header('Content-Disposition: attachment; filename="'.basename($file_name).'"');
  header('Content-Transfer-Encoding: binary');
  header('Content-Length: '.filesize($file_name));  // provide file size
  header('Connection: close');
  readfile($file_name);    // push it out
  exit();

}

?>