500 Internal Server Error

when I annotation this function my web is normal but when I logined then logout, and restart chrome its show 500 Internal Server Error? why?

>   following is my function:
> public function cookiesLogin(){
>         $salt = 'GYHZMFSWP';
>         $permanent  = $this->cookies->get('permanent')->getValue();
>         $identifier = $this->cookies->get('identifier')->getValue();
>        
>         $remember=RememberTokens::findFirstByIdentifier($identifier); //find data
> 
>         if($permanent == $remember->permanent){  //check cookie to login then setsession
>             if($identifier == md5($salt . md5($remember->getUser()->name .$salt))){
>                 if((time()-(86400*8))<$remember->createdAt){
>                     $user= Users::findFirstById($remember->userid );
>                     $this->regSessionAuth( $user );
>                     //reproduct cookie
>                     $this->rememberMe( $user );
>                     return true;
>                 }
>             }
>         }
> 
>         $this->cookies->get('permanent')->delete();
>         $this->cookies->get('identifier')->delete();
>         return false;
>     }
> 
>