I got this from for a login form tutorial:

function clean($str) {
        $str = @trim($str);
        if(get_magic_quotes_gpc()) {
            $str = stripslashes($str);
        }
        return mysql_real_escape_string($str);
    }

Could some one explain exactly what this does? I know that the 'clean' var is called up afterwards to sanitize the fields; I.e. $email = clean($_POST['email']);