WP_CLI\Formatter::format PHP Method

    private function format($items)
    {
        $fields = $this->args['fields'];
        switch ($this->args['format']) {
            case 'count':
                if (!is_array($items)) {
                    $items = iterator_to_array($items);
                }
                echo count($items);
                break;
            case 'ids':
                if (!is_array($items)) {
                    $items = iterator_to_array($items);
                }
                echo implode(' ', $items);
                break;
            case 'table':
                self::show_table($items, $fields);
                break;
            case 'csv':
                \WP_CLI\Utils\write_csv(STDOUT, $items, $fields);
                break;
            case 'json':
            case 'yaml':
                $out = array();
                foreach ($items as $item) {
                    $out[] = \WP_CLI\Utils\pick_fields($item, $fields);
                }
                if ('json' === $this->args['format']) {
                    echo json_encode($out);
                } else {
                    if ('yaml' === $this->args['format']) {
                        echo \Spyc::YAMLDump($out, 2, 0);
                    }
                }
                break;
            default:
                \WP_CLI::error('Invalid format: ' . $this->args['format']);
        }
    }