Sessions in PHP

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A session enables developers to keep track of information (variables) throughout various pages within a web application. The session serves to monitor user activity such as login status while simultaneously storing temporary data.

 

php-session

Why Use Sessions?

  • Store user data (e.g., name, email, role)
  • Track login/logout status
  • Preserve shopping cart contents
  • Avoid exposing data in URLs (like $_GET)

Starting a Session

Always call session_start() at the beginning of your script before any output:

 

<?php
session_start();
?>

Setting Session Variables

<?php
session_start();
$_SESSION["username"] = "Alice";
$_SESSION["role"] = "admin";
echo "Session variables are set.";
?>

Accessing Session Variables

<?php
session_start();
echo "Username: " . $_SESSION["username"];
echo "Role: " . $_SESSION["role"];
?>

Unset a Session Variable

 <?php
session_start();
unset($_SESSION["username"]);

Destroying a Session

<?php
session_start();
session_destroy();  // Deletes all session data
?>

Session vs Cookie

Feature Session Cookie
Stored Where Server Client (browser)
Secure? More secure Less secure
Size Limit Larger ~4KB
Lifespan Ends with browser or timeout Persistent (if set)

Session Function

Task Function
Start session session_start()
Set session $_SESSION['key'] = value;
Get session $_SESSION['key']
Unset session var unset($_SESSION['key']);
Destroy session session_destroy();
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