How to set & unset session variable in codeigniter ?

The session class in CodeIgniter allows the user to maintain a user’s “state” and track their activity while browsing the website. The session can be initialized using the library and auto-loaded in the environment using the following command.

$this->load->library('session');

Set the session variable: Session indexes can be assigned using key-value pairs. A particular key can be assigned to a value using the assignment operator. The value may be a string, key, or even an array. 

Syntax:

$_SESSION['key'] = value; 

Example 1:

PHP

<?PHP

  // Starting a new session
  session_start();

  $_SESSION['id'] = 9 ;

  // Check if the session name exists
  if( isset($_SESSION['id']) ) {
      echo 'Session id is '.$_SESSION['id'].'<br>';
  }
  else {
      echo 'Set the session id first '.'<br>';
  }
   echo'<br>';

  // Modifying the value of session
  $_SESSION['id'] = -8 ;
  echo 'New session id is '.$_SESSION['id'].'<br>';
?>

Output:

Session id is 9
New session id is -8

The session value can also be assigned using the set_userdata() method in CodeIgniter. This method takes a key as the first argument and the. next is the value to be assigned. 

Syntax:

set_userdata ('key' , value)

Multiple key-value pairs can also be added at the session index in CodeIgniter, indicated by the following code snippet.

Example 2:

PHP

<?php

  // Setting multiple key values
  $sess_arr = array('id'=>5, 'name' => 'yash');

  // Setting index at logged_in
  $this->session->set_userdata('logged_in', $sess_arr);

  // Printing the contents at this index
  print_r($_SESSION['logged_in']);
?>

Output:

Array ( [id] => 5 [name] => yash ) 

Unset the session variable: The session variable can be unset by assigning it to a NULL value. This destroys the value stored at this key value. 

Syntax:

$_SESSION['ey'] = NULL

Example 3:

PHP

<?php

  // Starting a new session
  session_start();

  // Setting multiple values
  $sess_arr = array('id'=>5, 'name' => 'yash');

  $_SESSION['logged_in']= $sess_arr;
  echo ('Old session : ');
  print_r ($_SESSION['logged_in']);
  echo '</br>';

  // Unsetting the value
  $_SESSION['logged_in']= NULL;
  echo ('New session? : ');
  print_r ($_SESSION['logged_in']);
?>

Output:

Old session : Array ( [id] => 5 [name] => yash )
New session? :