Drupal variable_set when resetting module admin form values

Question

I am trying to do a variable_set() when clicking 'Reset default values' on my module's admin page form. This runs through system_settings_form_submit(). The #default_value inside my form is reset, but my module relies on this stored variable to display some data. Clicking reset fills in the form with the default, but does not 'Save' it to recreate the variable in the database, so my module's function breaks. It appears that nothing happens after clicking Reset, other than it deleting the variable from the database. Thanks in advance.

My submit function looks like this:

function faculty_submit(&$form, &$form_state){
  if($form_state['values']['op'] == 'Reset to defaults') {
    global $faculty_detail_template_default;
    variable_set('faculty_detail_template', $faculty_detail_template_default);
  }
  elseif ($form_state['values']['op'] == 'Save configuration') {
  // Clear caches for list and detail pages.
  cache_clear_all('faculty_list', 'cache', TRUE);
  cache_clear_all('faculty_detail_load', 'cache', TRUE);
  }
}

Answer 1

First of all that's what system_settings_form_submit does when you press the Reset to defaults button. It calls variable_del which will delete all your defined variables in the form from the variables table.

Now your form's #default value is probably filled because you do something like this:

global $faculty_detail_template_default;
$form = array (
  '#default_value' => variable_get('faculty_detail_template', $faculty_detail_template_default),
);

I don't see why you insist of adding a default value in the variables table. This entire approach is flawed. Just use variable_get($name, $default) wherever your code depends on faculty_detail_template. That's precisely what the second parameter of this function is used for: $default The default value to use if this variable has never been set. So for Drupal, the absence of a variable from the variable table means it's up to the coder how to handle this case (provide a default for example). Default value which is specified using variable_get.

Second, if you used system_settings_form then you already have a submit function, the one mentioned above (system_settings_form_submit) so your faculty_submit won't be called unless you add it specifically to the array of submit callbacks to be executed. Something like this:

$form['#submit'][] = 'faculty_submit';
return system_settings_form($form); 

BTW, using global variables is a bad idea (in general) and you should try to avoid using them. That's what variables are used for :) Pieces of information which can be retrieved in different parts of the code. So instead add a .install file to your module and in that file you define these global variables using variable_set. This is a lot cleaner than just magically popping some global variables in the middle of the code.

Answer 2

you need to use &$form_state['values']['yourVariableNameOfForm'] instead of what I have made bold below.

variable_set('faculty_detail_template', $faculty_detail_template_default);