Drupal 7.36: form.inc 1471: form_execute_handlers($type, &$form, &$form_state): $function($form, $form_state); Does not work for static class method 'Drupal\mymodule\FormContoller::handler'

This problem is completely understood and an interim solution is suggested.

It can be considered a bug in the sense that form_execute_handlers($type, &$form, &$form_state) makes the "unwarranted" (i.e., not OO-friendly) assumption that a validation or submit handler (such as specified by $form['#validate']) can be a function but not a static class method.

It is a "Feature request" in the sense that a request is made for changes that better admit use of object-oriented techniques with Drupal7 forms.

Problem/Motivation

Because form_execute_handlers($type, &$form, &$form_state) uses $function($form, $form_state) on line 1471 (Drupal-7.25 form.inc), where $function is a named handler, it fails on callbacks to static handler methods of classes.

This makes it hard to use an encapsulating FormController with custom static handler methods; compare with the Drupal7 Page controller project.

If the handler function name $function is in the form "$class::$method" the call needs instead to be made by call_user_func_array($function,array($form,$form_state)).

function form_execute_handlers($type, &$form, &$form_state) {
...
  foreach ($handlers as $function) {
..
    }
    else {
      $function($form, $form_state);//1471 (Drupal-7.25 form.inc): fails for static class method.

If $function is a static class method that method is not found as a function, and PHP Fatal error: Call to undefined function is issued.

This is made clear at PHP manual: Variable functions and illustrated by the following PHP interactive session:

php > class Form { static public function validate($form,&$form_state) {echo "validate"; } }
php > $form = array();
php > $form_state = array();
php > $method='validate';
php > Form::$method($form,$form_state);
validate
php > $function = 'Form::validate';
php > $function($form,$form_state);
PHP Fatal error:  Call to undefined function Form::validate() in php shell code on line 1

Proposed resolution

I offer initially the following verbose solution, known to work for my own FormController static method case:

      //$function($form, $form_state);//ORIGINAL: fails for static class method

      //2013-01-03 Webel: also handle static class methods:
      $sep = '::';
      $is_static_method = strpos($function,$sep);
      if ($is_static_method) {
        call_user_func_array($function,array($form,$form_state));
      }
      else $function($form, $form_state);

The above enables one to encapsulate form validation and submit handlers, along with many other aspects of a form, in a FormController class, and thus promotes and supports more object-orientation already in Drupal7.

Remaining tasks

(reviews needed, tests to be written or run, documentation to be written, etc.)

I can perform tests as I am currently developing an entire object-oriented controller system for Drupal7, including form controllers (along with other object-oriented examples that integrate with Drupal7). However, I am not familiar with how other people might wish to use, for example, the $form['#validate'] for custom validation handlers, and whether other usages might break my simple test above, but I can't imagine anybody would use a validation function name with double-colon '::' in it unless they are also using a static class method handler.

TODO: Document the new capability to support static class method signatures as names handlers.

API changes

None, other than to document the new capability to support static class method signatures as named handlers.