See README.md.

README.md

This function is intended to be used within THEMENAME_preprocess_node() (or, well, any template_preprocess_node() implementation). It parses the field collection render array and gives you direct access to the render arrays of the individual deltas. They are normally buried in a few layers of arrays and normally require you to look up the field collection item ID/revision yourself first. Often, you simply want to iterate over them and don't care about their IDs. This helper function helps solve that problem.

You pass it the $variables array and the field names of the Field Collection fields that are attached to the node and that you want to massage. It adds variables to the $variables array, named after the field + _indexed.

So if you call THEMENAME_massage_field_collections($variables, array('field_my_field_collection');, $variables['field_my_field_collection'] will exist after it's done.

It also adds a #value and #revision_id property to the variable it creates, just in case you need to know those in your template for some reason.

template.php

<?php
/**
 * Adds (field name)_indexed items to the $variables array containing just
 * the field collection deltas. This saves having to correlate the IDs to the
 * actual render arrays just to iterate over them.
 *
 * @param $variables The $variables array. See notes on $source.
 * @param $field_names An array of field collection field names that you want
 * processed. The value of this is ignored if $source === 'field', so you can
 * pass array() or NULL or whatever you want in that case.
 * @param string $source Tell the function what behavior you expect, since
 * you might call it from a node or field preprocess hook. Possible values:
 *   - 'node': $variables is from a node preprocess function, and $field_names
 *     is an array of field collection field names.
 *   - 'field': $variables is from a field preprocess function, and
 *     $field_names doesn't matter (we overwrite it).
 *   - 'field_children' (not yet implemented): $variables is from a field
 *     preprocess function, and $field_names is an array of field collection
 *     field names attached to the field collection itself (not a node). This
 *     mode of operation massages the underlying fields instead of the field
 *     itself. Similar in concept to 'node'.
 */
function THEMENAME_massage_field_collections(&$variables, $field_names, $source = 'node') {
  // We need to know what to expect $variables to contain.
  // The logic is mostly the same, so we just hook up $content and $field_names
  // appropriately for each case.
  switch ($source) {
    // Called from the field itself, and should massage its own deltas.
    case 'field':
      $element = $variables['element'];
      // So we can avoid doing a bajillion isset() checks.
      if (THEMENAME_element_is_field_collection($element)) {
        // We fake the content array so that when the code below checks for
        // $content[$field_name], it finds the contents of $element.
        $content = array(
          $element['#field_name'] => $element,
        );

        $field_names = array($element['#field_name']);
      }
      break;

    // Called from the field, but we want to massage attached field collections.
    // $field_names must contain their names.
    case 'field_children':
      // TODO: Write this when it's needed.
      break;

    // Called from a node preprocess function.
    case 'node':
      $content = $variables['content'];
      break;
  }

  foreach ($field_names as $field_name) {
    $field_name_indexed = $field_name . "_indexed";

    $field_is_set = FALSE;

    switch ($source) {
      case 'field';
        // If we have element, we have the field for our purposes here.
        $field_is_set = isset($content[$field_name]);
        break;
      case 'field_children':
      case 'node':
        // In this case it's actually in the variables array. We don't use it,
        // but we just check that it actually has any values like this.
        $field_is_set = isset($variables[$field_name]);
        break;

    }

    if ($field_is_set) {
      // Get the actual deltas from #items, since they might not start at 0
      $deltas = element_children($content[$field_name]['#items']);
      foreach ($deltas as $record) {
        $value = $content[$field_name]['#items'][$record]['value'];
        $revision_id = $content[$field_name]['#items'][$record]['revision_id'];
        $variables[$field_name_indexed][$record] = $content[$field_name][$record]['entity']['field_collection_item'][$value];
        $variables[$field_name_indexed][$record]['#value'] = $value;
        $variables[$field_name_indexed][$record]['#revision_id'] = $revision_id;
      }
    }
  }
}

/**
 * Is this a field_collection-type field?
 * NOTE: We aren't checking if it's a field_collection_item entity. We are
 * checking for an element structure matching a field collection field, the
 * thing that gets attached to a node.
 */
function THEMENAME_element_is_field_collection($element) {
  if (isset($element) && isset($element['#bundle']) && isset($element['#field_name']) && isset($element['#field_type']) && $element['#field_type'] === 'field_collection') {
    return TRUE;
  }
  return FALSE;
}
?>