CI_DB_query_builder::order_by PHP Method

    public function order_by($orderby, $direction = '', $escape = NULL)
    {
        $direction = strtoupper(trim($direction));
        if ($direction === 'RANDOM') {
            $direction = '';
            // Do we have a seed value?
            $orderby = ctype_digit((string) $orderby) ? sprintf($this->_random_keyword[1], $orderby) : $this->_random_keyword[0];
        } elseif (empty($orderby)) {
            return $this;
        } elseif ($direction !== '') {
            $direction = in_array($direction, array('ASC', 'DESC'), TRUE) ? ' ' . $direction : '';
        }
        is_bool($escape) or $escape = $this->_protect_identifiers;
        if ($escape === FALSE) {
            $qb_orderby[] = array('field' => $orderby, 'direction' => $direction, 'escape' => FALSE);
        } else {
            $qb_orderby = array();
            foreach (explode(',', $orderby) as $field) {
                $qb_orderby[] = $direction === '' && preg_match('/\\s+(ASC|DESC)$/i', rtrim($field), $match, PREG_OFFSET_CAPTURE) ? array('field' => ltrim(substr($field, 0, $match[0][1])), 'direction' => ' ' . $match[1][0], 'escape' => TRUE) : array('field' => trim($field), 'direction' => $direction, 'escape' => TRUE);
            }
        }
        $this->qb_orderby = array_merge($this->qb_orderby, $qb_orderby);
        if ($this->qb_caching === TRUE) {
            $this->qb_cache_orderby = array_merge($this->qb_cache_orderby, $qb_orderby);
            $this->qb_cache_exists[] = 'orderby';
        }
        return $this;
    }