title: Codeigniter session is not working on PHP 7
body: <p>I am using <strong>codeigniter version 3.0.6</strong> on <strong>PHP 5.6</strong> and it works fine. but when I run same project on <strong>PHP 7.1</strong> , codeigniter session is not working. I set session like below</p>
  
  <pre><code>$login_session = $this-&gt;session-&gt;set_userdata("user_session",$session_data);
  </code></pre>
  
  <p>when I print  <strong>$login_session</strong>  it is blank on PHP 7</p>