$filename = $_GET['c'];

// 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 ( $file_extension == 'zip' ) {  

if( $filename == "" ) 
{
  echo "<html><title>..{ erro }..</title><body>Ficheiro não encontrado</body></html>";
  exit;
} elseif ( ! file_exists( $filename ) ) 
{
  echo "<html><title>..{ erro }..</title><body>Ficheiro não encontrado</body></html>";
  exit;
};
switch( $file_extension )
{
  case "pdf": $ctype="application/pdf"; break;
  case "zip": $ctype="application/zip"; 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();

} else {

print "<html><title>..{ erro }..</title><body>Ficheiro não permitido</body></html>";


}