CI_DB_forge::add_field PHP Method

    public function add_field($field)
    {
        if (is_string($field)) {
            if ($field === 'id') {
                $this->add_field(array('id' => array('type' => 'INT', 'constraint' => 9, 'auto_increment' => TRUE)));
                $this->add_key('id', TRUE);
            } else {
                if (strpos($field, ' ') === FALSE) {
                    show_error('Field information is required for that operation.');
                }
                $this->fields[] = $field;
            }
        }
        if (is_array($field)) {
            $this->fields = array_merge($this->fields, $field);
        }
        return $this;
    }