Another sessions question

I have a login, registration, update, and a form if you forget your password. I am using sessions to control the login and error messages. So this is my problem When a user enters the login page a session is started, if the user enters the wrong login info they will get an error message which is set in a session variable called $error['whatever'] (this will change depending on the error). If the user then decides he should register first, and goes to the register page - he gets a message on the page that simply says 'Array'. This is because the session is still active and $error['whatever'] is still set, although I've cleared the array with - $error = array(); On each page I have something like if($error) { echo $error['whatever']; }. I have used done it this way to make things more uniform and understandable, but I may also have shot myself in the foot - is there a way to get around this without having to change the session variables for each of these pages. I hope I have explained this properly, or for that matter used sessions properly - I am still trying to learn about sessions and problems like this keep popping up. TIA