update setting all fields to zero

[eluser]mflammia[/eluser]
Hi,

When updating a record using the code below it seems to replace all items with a 0?

Code:

function update_recordP($updateID,$person)
{
  $this->db->where ('id_person',$updateID);
                $this->db->update('person', $person);
                $str = $this->db->last_query();
                echo $str;
  return;
}

The echo $str looks like the following:

Code:

UPDATE `person` SET `first_name` = 'Joe', `second_name` = 'Bloggs', `dob` = '1972-08-11', `phone` = '', `email` = '' WHERE `id_person` = '5'

Code:

+-------------+-------------+------+-----+---------+----------------+
| Field       | Type        | Null | Key | Default | Extra          |
+-------------+-------------+------+-----+---------+----------------+
| id_person   | int(11)     | NO   | PRI | NULL    | auto_increment |
| first_name  | varchar(50) | YES  |     | NULL    |                |
| second_name | varchar(50) | YES  |     | NULL    |                |
| dob         | date        | NO   |     | NULL    |                |
| email       | varchar(80) | YES  |     | NULL    |                |
| phone       | varchar(20) | YES  |     | NULL    |                |
+-------------+-------------+------+-----+---------+----------------+

Regardless of whats in the table, whether some fields have entries or are blank the update sets them all to zero's?

Any ideas?