str::lower PHP Method

    static function lower($str)
    {
        return mb_strtolower($str, 'UTF-8');
    }

 public function login($welcome = null)
 {
     if ($user = panel()->site()->user()) {
         go(panel()->urls()->index());
     }
     $message = l('login.error');
     $error = false;
     $form = panel()->form('login');
     $form->cancel = false;
     $form->save = l('login.button');
     $form->centered = true;
     if (r::is('post') and get('_csfr') and csfr(get('_csfr'))) {
         $data = $form->serialize();
         $user = site()->user(str::lower($data['username']));
         if (!$user) {
             $error = true;
         } else {
             if (!$user->hasPanelAccess()) {
                 $error = true;
             } else {
                 if (!$user->login(get('password'))) {
                     $error = true;
                 } else {
                     go(panel()->urls()->index());
                 }
             }
         }
     }
     if ($username = s::get('username')) {
         $form->fields->username->value = html($username, false);
     }
     return layout('login', array('meta' => new Snippet('meta'), 'welcome' => $welcome ? l('login.welcome') : '', 'form' => $form, 'error' => $error ? $message : false));
 }