Determines whether a protected file exists and sets the filename too.
string $name: The virtual file name. Can be a relative path. return string The full path where the file is if it is valid, FALSE otherwise.
protected function checkFile($name) {
$filename = $this
->getFullPath($name, $directory, $directory_mtime);
return file_exists($filename) && filemtime($filename) <= $directory_mtime ? $filename : FALSE;
}