changing object in loop in Datamapper ORM to save

[eluser]mak.gnu[/eluser]
I'm trying to save a long form in Codeigniter's Datamapper. I'm able to save the form if I pass the value like this

Code:

$t->brandName = $this->input->post('brandName');  
$t->specialNotes = $this->input->post('specialNotes');
$t->name = $this->input->post('name')

;

Now if I call the save method it works fine.

$t->save();

Since the form is big I tried to add object values in foreach

Code:

$a = get_object_vars($t);
foreach ($a['stored'] as $k => $val){
      $t->$k = $this->input->post("$k");
}

however if I call the $t->save() it doesn't work.
Any input into this.