src/Query.php
public function group($group)
    {
        // Case with comma-separated fields
        if (is_string($group) && !$this->isUnescapablePattern($group) && strpos($group, ',') !== false) {
            $group = explode(',', $group);
        }

        if (is_array($group)) {
            foreach ($group as $g) {
                $this->args['group'][] = $g;
            }

            return $this;
        }

        $this->args['group'][] = $group;

        return $this;
    }
public function group($group)
    {
        // Case with comma-separated fields
        if (is_string($group) && !$this->isUnescapablePattern($group) && strpos($group, ',') !== false) {
            $group = explode(',', $group);
        }

        if (is_array($group)) {
            foreach ($group as $g) {
                $this->args['group'][] = $g;
            }

            return $this;
        }

        $this->args['group'][] = $group;

        return $this;
    }
Implements GROUP BY functionality. Simply pass either field name
as string or expression.

@param mixed $group Group by this

@return $this