What is the significance of using $_SESSION variables in PHP for maintaining user authentication and how should they be properly implemented?

Using $_SESSION variables in PHP for maintaining user authentication is significant because they allow you to store user-specific information across multiple pages. This is essential for keeping users logged in securely without exposing sensitive data in the URL or form submissions. To properly implement this, you should start the session at the beginning of each page where authentication is required, store the user's authentication status in a session variable upon successful login, and check this variable on subsequent pages to ensure the user is authenticated. 

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

// Check if the user is logged in
if(isset($_SESSION['logged_in']) && $_SESSION['logged_in'] === true) {
    // User is authenticated
    echo "Welcome, ".$_SESSION['username']."!";
} else {
    // Redirect to login page if not authenticated
    header("Location: login.php");
    exit();
}
?>

Keywords

$_SESSION user authentication implementation security PHP

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