$data = array(
'item' => $post_array['employee_title'],
'campaign' => $this->session->userdata('campaign'),
'userid' => $this->session->userdata('userid')
);
$insertStr = $this->db->insert_string('titles', $data);
$sql = "INSERT IGNORE INTO", $insertStr);
$this->db->query($sql);
// or this one that escapes the data.
$this->db->query("INSERT IGNORE INTO titles(item, campaign, userid) VALUES ('" .
$this->db->escape($data['item']) . "', '" .
$this->db->escape($data['campaign']) . "', '" .
$this->db->escape($data['userid']) . "')");