checkCSRF($f3, $f3->get('HEADERS.Referer') ?: '/'); $current = $f3->get('SESSION.theme') ?: 'light'; $new_theme = ($current === 'light') ? 'dark' : 'light'; $f3->set('SESSION.theme', $new_theme); $f3->reroute($f3->get('HEADERS.Referer') ?: '/'); } }