Hi @Sum
Yes you can use flash to display errors.
https://docs.phalcon.io/en/latest/reference/flash.html
In my project I use it like this.
        $di->set(     
                'flashSession', function ()    
        {    
            return new Phalcon\Flash\Session(array(    
                'error' => 'alert alert-dismissable alert-danger',    
                'success' => 'alert alert-dismissable alert-success',    
                'notice' => 'alert alert-dismissable alert-info',    
            ));    
        }    
        );    
Then you can call    
    $this->flash->success("The post was correctly saved!");         
This
    'error' => 'alert alert-dismissable alert-danger',    
is a reference to the css class representing the error.
This line of code is an example from bootstrap error.