Merge pull request pressflow#10 from dawehner/form-callbable

Make it possible to use any kind of callable as submit handlers

includes/form.inc

@@ -817,7 +817,7 @@ function form_execute_handlers($type, &$form, &$form_state) {
   }
 
   foreach ($handlers as $function) {
-    if (function_exists($function))  {
+    if (is_callable($function))  {
       // Check to see if a previous _submit handler has set a batch, but
       // make sure we do not react to a batch that is already being processed
       // (for instance if a batch operation performs a drupal_execute()).
@@ -828,7 +828,7 @@ function form_execute_handlers($type, &$form, &$form_state) {
         $batch['sets'][] = array('form_submit' => $function);
       }
       else {
-        $function($form, $form_state);
+        call_user_func_array($function, array($form, &$form_state));
       }
       $return = TRUE;
     }