how to create new session to replace old session CodeIgniter - codeigniter

Question

Im set session when user login
user model
function cek(){
$username=$this->input->post('username');
$password=md5($this->input->post('password'));
$query=$this->db->query("select akun.*,profile.kelas, profile.jurusan FROM profile right JOIN akun ON profile.id_akun = akun.id_akun WHERE akun.username = '$username' AND akun.password = '$password'");
if ($query->num_rows() > 0)
foreach ($query->result() as $data) {
$data=array('LOGIN'=>TRUE,'LEVEL'=>$data->level,'KELAS'=>$data->kelas,'JURUSAN'=>$data->jurusan,'ID_AKUN'=>$data->id_akun,'USERNAME'=>$data->username);
$this->session->set_userdata($data);
echo json_encode(array("status" => TRUE));
} else {
echo json_encode(array("status" => FALSE));
}
}
I want replace just session KELAS and JURUSAN
profile Controller
public function tambahprofile()
{
if($this->session->userdata('LOGIN')=='TRUE' and $this->session->userdata('LEVEL')==1 )
{
$id_akun=$this->session->userdata('ID_AKUN');
$kelas='12';
$jurusan='multimedia';
$this->validasi();
$data = array(
'nis' =>$this->input->post('nis'),
'id_akun' =>$id_akun,
'nama' =>$this->input->post('nama'),
'telpon' =>$this->input->post('telpon'),
'alamat' =>$this->input->post('alamat'),
'tgllahir' =>$this->input->post('tgllahir'),
'tmptlahir' =>$this->input->post('tmptlahir'),
'jurusan' =>$this->input->post('jurusan'),
'kelas' =>$this->input->post('kelas'),
'jk' =>$this->input->post('jk'),
);
if ($this->input->post('id')=='') {
$this->profile_model->tambah($data);
/**
TODO:
- First todo item
- Second todo item
*/
echo json_encode(array("status" => TRUE));
}else{
$this->profile_model->update(array('id' => $this->input->post('id')),$data);
$this->profile_model->update($data);
echo json_encode(array("status" => TRUE));
}
}else {
redirect('beranda/loginPage');
}
}
View
<?php echo $this->session->userdata('KELAS').$this->session->userdata('JURUSAN');?>
I'm create new session to replace old session KELAS and jurusan
no error but in my view is old session

Answer 1

Try this.
$data = array(
'kelas' => "test1",
'jurusan' => "Test2"
);
$this->session->set_userdata($data);
var_dump($this->session->userdata() );
$this->session->unset_userdata('kelas');
$data = array( 'kelas' => "newTest" );
$this->session->set_userdata($data);
var_dump($this->session->userdata() );
Using $this->session->unset_userdata( 'kelas' ); will unset only that entry.
$data = array( 'kelas' => "newTest" ); $this->session->set_userdata($data); will replace only that entry.
On a side note $password=md5( $this->input->post( 'password' ) ); this is not advised mate. If you read around that speed in which md5() can be broken make it a bad option for storing passwords.
PHP has a built in hashing function password_hash()
http://php.net/manual/en/function.password-hash.php
Would be worth a read.

Answer 2

when you need to replace old data just unset previous data and then set again your new data
//remove old data
$perticular_data = array('KELAS'=>$kelas,'JURUSAN'=>$jurusan);
$this->session->unset_userdata($perticular_data);
//set new data
$perticular_data = array('KELAS'=>$new_kelas,'JURUSAN'=>$new_jurusan);
$this->session->set_userdata($perticular_data);