what is session?

A session is a server-side storage mechanism that maintains user data across multiple HTTP requests.

How Sessions Work:

// Start a session
session_start();

// Store data in session
$_SESSION["username"] = "john_doe";
$_SESSION["user_id"] = 123;
$_SESSION["role"] = "admin";

// Access session data
echo "Welcome " . $_SESSION["username"];

// Check if session variable exists
if (isset($_SESSION["user_id"])) {
    echo "User is logged in";
}

// Destroy session
session_destroy();

Session Configuration:

// Set session parameters
ini_set("session.cookie_lifetime", 3600); // 1 hour
ini_set("session.gc_maxlifetime", 3600);
ini_set("session.cookie_secure", 1); // HTTPS only
ini_set("session.cookie_httponly", 1); // No JavaScript access

// Custom session handler
session_set_save_handler(
    "session_open",
    "session_close", 
    "session_read",
    "session_write",
    "session_destroy",
    "session_gc"
);

Benefits: Server-side security, larger storage capacity, automatic cleanup, cross-page data persistence.