Codeigniter save form_multiselect into database and set_value - php

Question

i try to save a form_multiselect but it dont save and the value dont select. I hope you can help me please.
Edit: Its working now but only with a single select. I cant select more as one options.
I try this
view
<div class="form-group">
<label class="col-sm-2 control-label" for="field-1"> Team</label>
<div class="col-sm-4">
<?= form_multiselect('teams_id[]', dd2menu('teams', array('teams_id' => 'title')), set_value('teams_id[]', $item->teams_id), 'class="form-control"') ?>
</div>
</div>
Controller
public function manage($id = NULL) {
$data = array();
if ($id) {
$this->{$this->model}->{$this->_primary_key} = $id;
$data['item'] = $this->{$this->model}->get();
if (!$data['item'])
show_404();
} else {
$data['item'] = new Std();
}
$this->load->library("form_validation");
$this->{$this->model}->custom_select = 'users.*, teams.title as teams';
$this->{$this->model}->joins = array( 'teams' => array('teams.teams_id = users.teams_id', 'inner'));
if ($this->form_validation->run() == FALSE)
$this->load->view($this->module . '/manage', $data);
else {
$this->users_model->teams_id = $this->input->post('teams_id');
$this->{$this->model}->save();
redirect('admin/' . $this->module);
}
}
Model
class Users_model extends CI_model
{
public $_table = 'users';
public $_primary_keys = array('user_id');
}
I cant find the error because its working if i one select. But i can select more as one options.

Answer 1

If found the fix in the other code from NikuNi.
Now its save 1 or 1,2 in the Database.
Controller
if( is_array( $this->input->post('teams_id') ) ) {
$this->{$this->model}->teams_id = join(",", $this->input->post('teams_id'));
} else {
$this->{$this->model}->teams_id = $this->input->post('teams_id');
}
$this->form_validation->set_rules('teams_id[]', 'teams_id', 'trim');