Comma separated list

Hi all

I've moved on to learning checking forms for valid imput and when doing thing 
that are repetive, like

if ($_POST['first'] == "") {  
       $errors .= 'Please enter a valid name.';
     }
if ($_POST['second'] == "") {  
       $errors .= 'Please enter a valid name.';
     }

I can think of a slightly better way like

if($_POST['first'] || $_POST['second'] || $_POST['third'] ==){
bla bla
}

I think I could also use empty(), not sure though, But I belive there are much 
easier ways. What would anyone here do?

If it were me, I'd use the one that uses the or operator.

David M.