# Editing Node Form Breaks

On a website i am currently working on in drupal, on one of the node edit forms, I have a validate function: like so:

$zip_code =$form_state['values']['submitted']['field_address']['postal_code'];
if(!preg_match("/^([a-ceghj-npr-tv-z]){1}[0-9]{1}[a-ceghj-npr-tv-z]{1}[0-9]{1}[a-ceghj-npr-tv-z]{1}[0-9]{1}$/i",$zip_code)) {