Learn > Advanced Higher Computing Science > AH Web Course > 2. Session Variables

PHP Session Variables

When you move from one web page to another, information stored in normal variables is lost.

A session allows a website to store information about a user and use it across multiple pages.

Sessions can be used to:

  • Remember if a user has logged in
  • Store a user’s ID
  • Remember items in a shopping basket
  • Keep a user’s score across several pages

Starting a Session

Before using session variables, the session must be started:

<?php 
    session_start(); 
?>

session_start() should be placed at the top of the page before any HTML.

Every page that needs to access the session must include session_start().

Creating a Session Variable

Session variables are stored using $_SESSION.

For example:

$_SESSION["loggedIn"] = true;

This creates a session variable called loggedIn and gives it the value true.

Unlike a normal variable, this value can be accessed from other pages on the website.

Using Sessions for Login

A website could check a username and password:

$username = $_POST["username"]; 
$password = $_POST["password"]; 
if ($username == "admin" && $password == "pass123") 
{ 
    $_SESSION["loggedIn"] = true; 
}

The session variable is only created when the correct login details are entered.

Checking a Session Variable

isset() can be used to check whether a session variable has been created:

if (isset($_SESSION["loggedIn"])) 
{ 
    echo "You are logged in."; 
} 
else 
{ 
    echo "You must login to view this page."; 
}

In this example isset($_SESSION[“loggedIn”]) checks whether the loggedIn session variable exists.

This can be used to protect pages that should only be viewed by logged-in users.

Ending a Session

When a user logs out, the session can be ended.

session_start();

session_destroy();

session_start() accesses the user’s current session.

session_destroy() then destroys the session and the information stored in it.

Button TextButton Text