Why wouldn't hook_form_submit be called? function mymodule_reviewer_node_form($node, &amp;$form_state) {
global $school;
if ($school) {
    $form['field_reviewer_school']['#value'] = array(array('nid' =&gt; $school));
    $form['field_reviewer_school']['#access'] = FALSE;
}
  return $form;
}

function mymodule_reviewer_node_form_submit($node, &amp;$form_state) {
}


The form gets submitted successfully, but form_submit never gets called. What might cause this?
The form should be:

   function  mymod_reviewer_node_form($form_state) {
     $form = array();

     // Build the form...

     return $form;
   }


The submit handler should be:

   function mymod_reviewer_node_form_submit($form, &amp;$form_state) {
     // Do something with $form_state['values'] or whatever
   }


And make sure that whatever is rendering the form passes through drupal_get_form().

Finally, one tricky bit: Make sure you are not accidentally overriding a hook. mymod_form(), for example, implements hook_form(), which is probably not what you really intend to do.

I find that nine times out of ten, if the submit handler is not being called, it's because I named the function incorrectly.