Drupal 6: hook_form_node_form_alter() not working

I've long known about the versatile hook_form_alter() function, which allows you to alter any form before it gets displayed on the page, using your own custom module. Recently I discovered the wonderful hook_form_FORM_ID_alter() function, which is only fired for a specific form id, making it a better solution when you want to target only 1 form.

I had used this successfully a few times, and then hit a wall when I tried using it for the main node edit form (the form's id is node-form, so I called the function hook_form_node_form_alter). Half an hour later, I stumbled upon the solution: it does not want the HTML ID attribute, it wants the internal Drupal ID for the form. So in my custom module, I used this code to get the ID:

function MODULE_form_alter(&$form, &$form_state, $form_id) {
 echo "formID=".$form_id;
}

Which turned out to be page_node_form, so the final function that worked was called MODULE_form_page_node_form_alter().

REFERENCES
http://www.hashbangcode.com/blog/drupal-hookformalter-node-form-501.html