protected function find_handler_path($filename) {
	$filename = strtolower($filename);
	
	if (preg_match('{[^a-z0-9/_-]}', $filename)) {
		return false;
	}
	
	$base_path = \alsvanzelf\fem\ROOT_DIR_APP.$this->handler_base_path.'/';
	$full_path = $base_path.$filename.'.php';
	if (file_exists($full_path) == false) {
		return false;
	}
	
	// sanity check to prevent escaping outside the base dir
	if (strpos($full_path, $base_path) !== 0) {
		return false;
	}
	
	return $full_path;
}