Determine whether a field has changed during hook_node_submit

Question

Basically I need a way of checking whether a node field changed during some event hook...I am using hook_node_submit() but this doesn't seem to work:

$form['field_status']['und']['#value'] !== $node->field_status['und'][0]['value']

Produces equality all the time...any suggestions on which hook and how I would check equality when I know a value has changed it should fire off an email...

Alex

Answer 1

As said from @Clive, the only way is to compare the value in $node with the value contained in $node->original.

As far as I can see, that value is only available in hook_node_update(), hook_node_presave() and every hook invoked from node_save() which receive the saved node as argument (but only when a node is updated), since entity_load_unchanged() is called from node_save() (which also unset $node->original before exiting). If you need it in hook_node_submit() you could simply add the following code in your implementation.

if (!empty($node->nid) && !isset($node->original)) {
  $node->original = entity_load_unchanged('node', $node->nid);
}

Since you are checking for field properties, the other, more general, hook would be hook_field_attach_submit(hook_field_attach_submit($entity_type, $entity, $form, &$form_state)). With this hook, $entity would contain the field value before the node has been edited, and $form_state contains the submitted values.