showing only allowed files and folders in the file manager

well... I'm trying to post the code, but it seems PHP code is not accepted. THe server returns a 406 Not acceptable error

Not Acceptable

An appropriate representation of the requested resource /forums/posting.php could not be found on this server.
Apache/2.2.0 (Fedora) mod_auth_passthrough/2.1 mod_bwlimited/1.4 PHP/5.2.5 Server at www.fckeditor.net Port 80

function ValidateGotFolderOrFile ($path) {
   global $Config;
   $info = pathinfo($path);

   if (is_dir($path)) {
      foreach($Config['NotListedFolders'] as $Mask) 
         if (preg_match ("/$Mask/", Substr($path, strlen($Config['UserFilesAbsolutePath'])+1))) return false;
      return true;
   }

   if (in_array($info['extension'],  $Config['NotListedFilesByExtension'])) return false;

   foreach ($Config['NotListedFilesByMask'] as $Mask) {
      if (preg_match($Mask, basename($path))) return false;
   }

   if (in_array($info['extension'], $Config['ListedFilesByExtension'] + $Config['AllowedExtensions']['File'])) 
      return true;

   return false;
}


function GetFolders( $resourceType, $currentFolder )
{
   // Map the virtual path to the local server path.
   $sServerDir = ServerMapFolder( $resourceType, $currentFolder, 'GetFolders' ) ;

   // Array that will hold the folders names.
   $aFolders   = array() ;

   $oCurrentFolder = opendir( $sServerDir ) ;

   while ( $sFile = readdir( $oCurrentFolder ) )
   {
      if ( $sFile != '.' && $sFile != '..' && is_dir( $sServerDir . $sFile )  && ValidateGotFolderOrFile ( $sServerDir . $sFile ) )
      $aFolders[] = '<Folder name="' . ConvertToXmlAttribute( $sFile ) . '" />' ;
   }

   closedir( $oCurrentFolder ) ;

   // Open the "Folders" node.
   echo "<Folders>" ;

   natcasesort( $aFolders ) ;
   foreach ( $aFolders as $sFolder )
      echo $sFolder ;

   // Close the "Folders" node.
   echo "</Folders>" ;
}


function GetFoldersAndFiles( $resourceType, $currentFolder )
{
   // Map the virtual path to the local server path.
   $sServerDir = ServerMapFolder( $resourceType, $currentFolder, 'GetFoldersAndFiles' ) ;

   // Arrays that will hold the folders and files names.
   $aFolders   = array() ;
   $aFiles      = array() ;

   $oCurrentFolder = opendir( $sServerDir ) ;

   while ( $sFile = readdir( $oCurrentFolder ) )
   {
      if ( $sFile != '.' && $sFile != '..' && ValidateGotFolderOrFile ("$sServerDir{$sFile}"))
      {
         if ( is_dir( $sServerDir . $sFile ) )
            $aFolders[] = '<Folder name="' . ConvertToXmlAttribute( $sFile ) . '" />' ;
         else
         {
            $iFileSize = @filesize( $sServerDir . $sFile ) ;
            if ( !$iFileSize ) {
               $iFileSize = 0 ;
            }
            if ( $iFileSize > 0 )
            {
               $iFileSize = round( $iFileSize / 1024 ) ;
               if ( $iFileSize < 1 ) $iFileSize = 1 ;
            }

            $aFiles[] = '<File name="' . ConvertToXmlAttribute( $sFile ) . '" size="' . $iFileSize . '" />' ;
         }
      }
   }

   // Send the folders
   natcasesort( $aFolders ) ;
   echo '<Folders>' ;

   foreach ( $aFolders as $sFolder )
      echo $sFolder ;

   echo '</Folders>' ;

   // Send the files
   natcasesort( $aFiles ) ;
   echo '<Files>' ;

   foreach ( $aFiles as $sFiles )
      echo $sFiles ;

   echo '</Files>' ;
}

// Besides the extensions in $Config['AllowedExtensions']['File'], show the files with the 
// next extensions:
$Config['ListedFilesByExtension'] = array('php', 'php3', 'phtml');

// Excepto for the ones with these extensions (for blocking some of the included in 
// the $Config['AllowedExtensions']['File'] array)
$Config['NotListedFilesByExtension'] = array ('css', 'htc', 'js', 'htaccess', 'flv', 'swf', 'fla');

// And except for the files whose names would match the following preg_match patterns:
$Config['NotListedFilesByMask'] = array('/tests?\.php/');
// Hidden folders (preg_match'ing them):
$Config['NotListedFolders'] = array( '^admin$', '^core$','^rest$');

Well, it seems I've got around the problem. For the webmaster: I did it by capitalizing the "Substr" function. I had typed it with "s", but it seems the server doestn't like it so much (I can't even putting here "s-u-b-s-t-r"! I got another 406 error)