Putting @ in front of the filetype() function does not prevent it from raising a warning (Lstat failed), if E_WARNING is enabled on your error_reporting.
The most common cause of filetype() raising this warning and not showing a filetype() in the output (it actually returns NULL) is, if you happened to pass just the 'Dir or File Name' and not the complete "Absolute or Relative Path" to that 'file or Dir'. It may still read that file and return its filetype as "file" but for Dir's it shows warning and outputs NULL.
$pathToFile = '/var/www';
$file = 'test.php';
$dir = 'somedir';
Output for filetype($file) will be returned as 'file' and possibly without any warning, but for filetype($dir), it will return NULL with the warning "Lstat failed", unless you pass a complete path to that dir, i.e. filetype($pathToFile.'/'.$dir).
This happened to me and found this solution after a lot of trial and error. Thought, it might help someone.