codeigniter session user_data being reset - php

Question

I am using Codeigniter database session. I have a search navigation on the header of my page which contains a search from and to date and a text field.
I also have pagination on the page. I am using a custom controller (MY_Controller) and I am setting the from and to dates here. See below.
public function __construct()
{
parent::__construct();
$this->load->model('News_model');
$this->set_dates();
}
function set_dates()
{
if (empty($this->input->post('from_date')))
{
$this->session->set_userdata('sel_from_date', date('Y-m-d'));
}
else
{
if($_SERVER['REQUEST_METHOD'] == "POST")
{
$this->session->set_userdata('sel_from_date', $this->input->post('from_date'));
}
}
if (empty($this->input->post('to_date')))
{
$this->session->set_userdata('sel_to_date', date('Y-m-d'));
}
else
{
if($_SERVER['REQUEST_METHOD'] == "POST")
{
$this->session->set_userdata('sel_to_date', $this->input->post('to_date'));
}
}
}
This works fine even when I enter dates in the from and/or to fields and click submit, the correct dates stay in the search fields.
However when I click on the link for the next page (in pagination) which basically adds another segment to the URL (i.e. mysite/news/politics/1) and loads the page, the dates in the session user_data are reset. I thought maybe the logic above for blank input dates was being executed again in this instance but that is not the case.
HTML:
<div class="form-group">
<label for="from_date" class="col-sm-2 control-label">From Date:</label>
<div class="col-sm-6">
<input type="text" placeholder="From Date" class="form-control" name="from_date" id="from_date" width=10" value="<?php echo $this->session->userdata('sel_from_date'); ?>" />
</div>
</div>
<div class="form-group">
<label for="to_date" class="col-sm-2 control-label">To Date:</label>
<div class="col-sm-6">
<input type="text" placeholder="To Date" class="form-control" name="to_date" id="to_date" value="<?php echo $this->session->userdata('sel_to_date'); ?>" />
</div>
</div>
<div class="form-group">
<input type="text" class="form-control" placeholder="Search">
<button type="submit" class="btn btn-default" name="go" id="go">Go</button>
</div>

Answer 1

Check whether the session variable 'sel_from_date' is already set .
If yes don't set it again. Try below in your controller:
if($this->session->userdata('sel_from_date') != '')
{
// Do not set the session variable 'sel_from_date'
}
else
{
// Execute the function $this->set_dates()
}

Answer 2

I resolved the issues with the following code.
if (empty($this->input->post('from_date')) && !$this->session->userdata('sel_from_date'))
{
....
}