Drupal multiple field : Add new item on top of the list

drupal_multiple_field_add_to_top.php

<?php

// Insert new item on top of the list.
// Display file input first for better UI (https://lut.im/0AkZwIQOUa/dtzEPerqgp3hQ3hk.png) 


// In a .module


/**
 * Implements hook_field_attach_form().
 * Inspired from add_to_top contrib module
 */
function MYMODULE_field_attach_form($entity_type, $entity, &$form, &$form_state, $langcode = NULL) {
  if (isset($form['#entity_type']) && isset($form['#bundle'])) {
    // Get all field instances on this bundle.
    $field_info_instances = field_info_instances($form['#entity_type'], $form['#bundle']);
    // Iterate over each instance.
    foreach ($field_info_instances as $field_name => $field_info_instance) {
      if ($field_name == 'field_my_multiple_field' && isset($form[$field_name])) {

        $langcode = $form[$field_name]['#language'];
        // Make a reference to the position in the array.
        $field = &$form[$field_name][$langcode];

        // First get the delta of the new (last) item.
        $max = max(array_keys($field));

        // Set the _weight to -100 so its always at the top.
        $field[$max]['_weight']['#default_value'] = -100;
        $field[$max]['#weight'] = -100;
      }
    }
  }
}



// In the theme's template.php file


/**
 * Override theme_file_widget_multiple().
 */
function MYTHEME_file_widget_multiple($variables) {
  $element = $variables['element'];

  if ($element['#field_name'] != 'field_my_multiple_field') {
    // Default theme function
    return theme_file_widget_multiple($variables);
  }
  else {
    // Note: Same as theme_file_widget_multiple() default function except that
    // the items table is render at the end

    // Special ID and classes for draggable tables.
    $weight_class = $element['#id'] . '-weight';
    $table_id = $element['#id'] . '-table';

    // Build up a table of applicable fields.
    $headers = array();
    $headers[] = t('File information');
    if ($element['#display_field']) {
      $headers[] = array(
        'data' => t('Display'),
        'class' => array('checkbox'),
      );
    }
    $headers[] = t('Weight');
    $headers[] = t('Operations');

    // Get our list of widgets in order (needed when the form comes back after
    // preview or failed validation).
    $widgets = array();
    foreach (element_children($element) as $key) {
      $widgets[] = &$element[$key];
    }
    usort($widgets, '_field_sort_items_value_helper');
    
    $rows = array();

    foreach ($widgets as $key => &$widget) {
      // Save the uploading row for last.
      if ($widget['#file'] == FALSE) {
        $widget['#title'] = $element['#file_upload_title'];
        $widget['#description'] = $element['#file_upload_description'];
        continue;
      }

      // Delay rendering of the buttons, so that they can be rendered later in the
      // "operations" column.
      $operations_elements = array();
      foreach (element_children($widget) as $sub_key) {
        if (isset($widget[$sub_key]['#type']) && $widget[$sub_key]['#type'] == 'submit') {
          hide($widget[$sub_key]);
          $operations_elements[] = &$widget[$sub_key];
        }
      }

      // Delay rendering of the "Display" option and the weight selector, so that
      // each can be rendered later in its own column.
      if ($element['#display_field']) {
        hide($widget['display']);
      }
      hide($widget['_weight']);

      // Render everything else together in a column, without the normal wrappers.
      $widget['#theme_wrappers'] = array();
      $information = drupal_render($widget);

      // Render the previously hidden elements, using render() instead of
      // drupal_render(), to undo the earlier hide().
      $operations = '';
      foreach ($operations_elements as $operation_element) {
        $operations .= render($operation_element);
      }
      $display = '';
      if ($element['#display_field']) {
        unset($widget['display']['#title']);
        $display = array(
          'data' => render($widget['display']),
          'class' => array('checkbox'),
        );
      }
      $widget['_weight']['#attributes']['class'] = array($weight_class);
      $weight = render($widget['_weight']);

      // Arrange the row with all of the rendered columns.
      $row = array();
      $row[] = $information;
      if ($element['#display_field']) {
        $row[] = $display;
      }
      $row[] = $weight;
      $row[] = $operations;
      $rows[] = array(
        'data' => $row,
        'class' => isset($widget['#attributes']['class']) ? array_merge($widget['#attributes']['class'], array('draggable')) : array('draggable'),
      );
    }

    drupal_add_tabledrag($table_id, 'order', 'sibling', $weight_class);

    $output = '';

    // Magic happens here.
    // File input element first
    $output .= drupal_render_children($element);
    // Then items table
    $output .= empty($rows) ? '' : theme('table', array('header' => $headers, 'rows' => $rows, 'attributes' => array('id' => $table_id)));
    
    return $output;
  }
}