SortByFieldTwigExtension.php

<?php
/**
 * User: Victor Häggqvist
 * Date: 3/4/15
 * Time: 2:07 AM
 *
 * The base of the filter is borrowed from https://github.com/dannynimmo/craftcms-sortbyfield
 *
 * I hav extended it to also sort array structures
 */

class   SortByFieldTwigExtension extends \Twig_Extension
{
  public function getName() {
    return 'sortbyfield';
  }

  public function getFilters() {
    return array(
      new \Twig_SimpleFilter('sortbyfield', array($this, 'sortByFieldFilter'))
    );
  }
  /**
   * The "sortByField" filter sorts an array of entries by the specified field's value
   *
   * Usage: {% for entry in master.entries|sortByField('ordering', 'desc') %}
   */
  public function sortByFieldFilter($content, $sort_by = null, $direction = 'asc') {
    if (!is_array($content)) {
      throw new Exception('Variable passed to the sortByField filter is not an array');
    } elseif ($sort_by === null) {
      throw new Exception('No sort by parameter passed to the sortByField filter');
    } elseif (!self::isSortable($content[0], $sort_by)) {
      throw new Exception('Entries passed to the sortByField filter do not have the field "' . $sort_by . '"');
    } else {
      // Unfortunately have to suppress warnings here due to __get function
      // causing usort to think that the array has been modified:
      // usort(): Array was modified by the user comparison function
      @usort($content, function ($a, $b) use($sort_by, $direction) {
        $flip = ($direction === 'desc') ? -1 : 1;

        if (is_array($a))
          $a_sort_value = $a[$sort_by];
        else
          $a_sort_value = $a->__get($sort_by);

        if (is_array($b))
          $b_sort_value = $b[$sort_by];
        else
          $b_sort_value = $b->__get($sort_by);

        if($a_sort_value == $b_sort_value) {
          return 0;
        } else if($a_sort_value > $b_sort_value) {
          return (1 * $flip);
        } else {
          return (-1 * $flip);
        }
      });
    }
    return $content;
  }

  /**
   * Validate the passed $item to check if it can be sorted
   * @param $item mixed Collection item to be sorted
   * @param $field string
   * @return bool If collection item can be sorted
   */
  private static function isSortable($item, $field) {
    if (is_array($item))
      return array_key_exists($field, $item);
    elseif (is_object($item))
      return $item->__isset($field);
    else
      return false;
  }
}