$action = filter_input(INPUT_GET, 'action');
$action=htmlspecialchars(trim($_GET['action'] ?? null))
$action=htmlspecialchars(trim($_GET['action'] ?? null))
$action = filter_input(INPUT_GET, 'action', FILTER_SANITIZE_SPECIAL_CHARS);
$action = filter_input(INPUT_GET, 'action', FILTER_SANITIZE_SPECIAL_CHARS);
$action = filter_input(INPUT_GET, 'action');