Codeigniter session not saving userdata and creating duplicate sessions

Codeigniter session not saving userdata and creating duplicate sessions

I'm trying to send my username and password through ajax to the database
for verifying the user but I see CI is creating duplicate sessions for a
single request. Also when I'm trying to set the userdata through
session->set_userdata it is not setting the data. This is confirmed as
neither firebug nor my session database shows the data. Also since no data
is getting set in the session I do not get anything back in my ajax
response to show in the ajax response success
Please guide me what am I doing wrong here as the session cookies are
created even if the username and password combination is wrong.
model
function validate_login()
{
$this->db->where('Useremail',$this->input->post('username'));
$this->db->where('Password',$this->input->post('password'));
$result = $this->db->get('users');
if ($result->num_rows == 1) {
return true;
}else{
return false;
}
}
controller
function validate_login_user()
{
$this->load->model('data_model');
if ($this->data_model->validate_login())
{
$data = array (
'username' => $this->input->post('username'),
'is_logged_in' => true
);
$this->session->set_userdata($data);
return = $this->session->userdata('username');
}
else
{
return false;
}
}
MY view
<script>
$(function(){
$('.login').click(function(){
var username = $('#username').attr('value');
var password = $('#password').attr('value');
if (username == "" || password == ""){
$('.LoginErrormsg').css('display','block');
}
if (username !== "" && password !== ""){
$.ajax({
url:"<?php echo site_url('home/validate_login_user');?>",
type:'POST',
data:{username:username,
password:password},
success:function(){
$('#sitelogin').html(msg);
$('.logout').css('display','block');
}
});
return false
}else{
return false;
}
});
})
<div id="sitelogin">
<input type="text" class="loginbox" name = "login_username" id =
"username" placeholder="Email address / Username" />
<input type="password" class="loginbox" name = "login_password"
id="password" placeholder="Password" />
<div class="LoginErrormsg">You forgot to enter Username and
Password</div>
<button class="login" name = "login">Login</button>
<button class="logout" name = "logout">Logout</button>
</div>