PHP Session Handling

PHP Session Handling – Storing User Data Across Pages 🗂️

Ever wondered how websites remember who you are after you log in? 🤔 That’s PHP sessions at work! Sessions allow you to store user data across multiple pages, making them essential for login systems, shopping carts, and more.

🔹 Starting a PHP Session

To start a session in PHP, use the session_start() function. This must be called at the **very beginning** of the script before any HTML output.

📝 Example: Starting a Session

<?php
session_start(); // Start the session
?>

Tip: Always call session_start() before outputting anything!

🔹 Storing and Retrieving Session Variables

Session variables are stored in the $_SESSION superglobal array.

📝 Example: Setting and Getting Session Data

<?php
session_start(); // Start session

// Set session variables
$_SESSION["username"] = "JohnDoe";
$_SESSION["role"] = "Admin";

// Retrieve session data
echo "Welcome, " . $_SESSION["username"] . "! Your role is: " . $_SESSION["role"];
?>

Output: Welcome, JohnDoe! Your role is: Admin

🔹 Checking If a Session Variable Exists

Use isset() to check if a session variable is set.

📝 Example: Checking Session Variables

<?php
session_start();

if (isset($_SESSION["username"])) {
    echo "User is logged in as: " . $_SESSION["username"];
} else {
    echo "No user is logged in.";
}
?>

🔹 Destroying a Session (Logout)

To log out a user, you must remove their session data.

📝 Example: Ending a Session

<?php
session_start();
session_unset(); // Remove session variables
session_destroy(); // Destroy session

echo "Session destroyed. User logged out.";
?>

Warning: After calling session_destroy(), session variables will no longer be accessible.

🎯 Key Takeaways

• session_start() → Must be called before any output.
• $_SESSION → Stores session variables.
• isset($_SESSION["var"]) → Checks if a session variable exists.
• session_unset() → Clears session variables.
• session_destroy() → Ends the session.

📝 Practice Time!

Modify the session example and try storing a shopping cart 🛒 or login system. Can you check if a user is logged in before displaying content? 🤔