Knp\Component\Pager\Event\Subscriber\Sortable\ArraySubscriber::items PHP Method

    public function items(ItemsEvent $event)
    {
        if (is_array($event->target) && count($event->target) > 1) {
            if (isset($_GET[$event->options['sortFieldParameterName']])) {
                $this->sortDirection = isset($_GET[$event->options['sortDirectionParameterName']]) && strtolower($_GET[$event->options['sortDirectionParameterName']]) === 'asc' ? 'asc' : 'desc';
                // TODO add whitelist
                //                if (isset($event->options['sortFieldWhitelist'])) {
                //                    if (!in_array($_GET[$event->options['sortFieldParameterName']], $event->options['sortFieldWhitelist'])) {
                //                        throw new \UnexpectedValueException("Cannot sort by: [{$_GET[$event->options['sortFieldParameterName']]}] this field is not in whitelist");
                //                    }
                //                }
                $sortFieldParameterName = explode('.', $_GET[$event->options['sortFieldParameterName']]);
                if (isset($sortFieldParameterName[1])) {
                    // Capitalize first letter in order to prepare getter construction
                    $sortFieldName = ucfirst($sortFieldParameterName[1]);
                    $this->currentSortingFieldGetter = "get{$sortFieldName}";
                    // Getter detection
                    $class = new ReflectionClass(get_class($event->target[0]));
                    if ($class->hasMethod($this->currentSortingFieldGetter)) {
                        // Sort
                        usort($event->target, array($this, "sort" . ucfirst($this->sortDirection)));
                    }
                }
            }
        }
    }