Sorting Field Collection Programmatically in Drupal 7

Question

How to change the order/weight of the items inside field collection programmatically when the node is saved? Any help is appreciated. Thank you.

Answer 1

Already found the answer. I'm using hook_node_presave and then reorder the field collection array. Previously I was using hook_node_update and it didn't work.

Answer 2

This is a code snippet for sorting a field collection by any of its fields before saving the node:

function your_module_node_presave($node){
  if ($node->type == 'foo') {
    // We must sort by this field collection field
    if (!empty($node->field_to_sort_by)) {

      // Get the values of the sorting field. We must load the fc items for this.
      $items = field_get_items('node', $node, 'field_to_sort_by');
      foreach ($items as $item) {
        $fc[] = field_collection_field_get_entity($item);
      }

      // field collection fields on nodes only contains 'value' and 'revision_id'.
      // We temporarily add the field to sort by, 
      // for using the convenient uasort() function over the array.
      $tmp_array = $node->field_to_sort_by[LANGUAGE_NONE];
      foreach ($tmp_array as $key => $item) {
        $tmp_array[$key]['sortfield'] = $fc[$key]->field_to_sort_by[LANGUAGE_NONE][0]['value'];
      }

      // Now we sort the node's field array using uasort().
      usort($tmp_array, 'my_module_sortByField_asc');

      // unset the sorting field before updating node's field collection
      foreach ($tmp_array as $key => $item) {
        unset($tmp_array[$key]['sortfield']);
      }

      $node->field_to_sort_by[LANGUAGE_NONE] = $tmp_array;
    }

  }
}

function my_module_sortByField_asc($a, $b) {
  return $a['sortfield'] - $b['sortfield'];
}