zend update is deleting old values - php

Question

I am doing update in zend which in some cases doesn't update all the fields, the fields that are not updated become null as if we are doing an add.
This is the code from the Controller
$result = $theuserModel->updateUserTest(
$id,
$this->getRequest()->getPost('user_name'),
/*some code*/
$this->getRequest()->getPost('user_postee')
);
if ($result) {
$this->view->notif = "Successfull Update";
return $this->_forward('index');
}
The corresponding model
public function updateUserRest($id, $nom,$poste)
{
$data = array(
'user_name' => $nom,
'user_postee' => $poste
);
$result=$this->update($data, 'user_id = '. (int)$id);
return $result;
}
I do an update for user_name only I found that the old value of user_postee got deleted and replaced by the default value (initial value which we get at the time of creation) for example null.
Thanks in advance!
I have done this changes (bad solution) If anyone has another one optimised
->Controller
if($this->getRequest()->getPost('user_name')){
$resultname=$userModel->updateUserName($id,$this-
>getRequest()->getPost('user_name'));
}
if($this->getRequest()->getPost('user_postee')){
$resultpostee=$userModel->updateUserPoste($id,$this-
>getRequest()->getPost('user_postee'));
}
if ($resultname|| $resultpostee){
$this->view->notif = "Mise à jour effectuée";
return $this->_forward('index');
}
-> Model
public function updateUserName($id, $name)
{
$data = array(
'user_name' => $name
);
$result=$this->update($data, 'user_id = '. (int)$id);
return $result;
}
public function updateUserPostee($id, $postee)
{
$data = array(
'user_postee' => $poste
);
$result=$this->update($data, 'user_id = '. (int)$id);
return $result;
}

Answer 1

that is complete correct response of update in Zend Db Table.
I believe your assumption is if the value of 'user_postee' is null then it should not be updated into the database, am I correct.
The answer is they will update the new value of "NULL" into the database.
To avoid it , what you should do is
using fetchrow() to get the value of the line by id
foreach user_name and user_postee check if the value of them matching the array value your fetched , if nothing changed or Null, then use the old value from array , if new value exist use new value insert into the array , finally use update to update the new array into database

Answer 2

Assume your Table Column is also "user_name" and "user_postee"
public function updateUserRest($id, $nom,$poste)
{
$row = $this->fetchRow('user_id = '. (int)$id);
if(!empty($nom) && $row['user_name'] != trim($nom)){
$row['user_name'] = $nom;
}
if(!empty($poste) && $row['user_poste'] != trim($poste)){
$row['user_poste'] = $poste;
}
$result=$this->update($row, 'user_id = '. (int)$id);
return $result;
}