Starting and using sessions in PHP

Introduction

Sessions help remember information about a user while they browse your website. This way, you can keep users logged in or save their preferences.

When you want to keep a user logged in across different pages.

When you need to save user choices like language or theme during their visit.

When you want to store temporary data like items in a shopping cart.

When you want to track user activity without asking them to log in again.

When you want to pass information between pages without showing it in the URL.

Syntax

PHP

<?php
session_start();
// Now you can use $_SESSION to store or get data
$_SESSION['key'] = 'value';
?>

You must call session_start() before any HTML or output.

Use the $_SESSION array to save or read session data.

Examples

Starts a session and saves the username 'Alice' in the session.

PHP

<?php
session_start();
$_SESSION['username'] = 'Alice';
?>

Starts the session and prints the saved username.

PHP

<?php
session_start();
echo $_SESSION['username'];
?>

Counts how many times the user has visited the page during the session.

PHP

<?php
session_start();
if (!isset($_SESSION['visits'])) {
    $_SESSION['visits'] = 1;
} else {
    $_SESSION['visits']++;
}
echo "Visit number: " . $_SESSION['visits'];
?>

Sample Program

This program counts how many times a user visits the page in one session. Each time the page reloads, the counter increases by one.

PHP

<?php
session_start();

if (!isset($_SESSION['counter'])) {
    $_SESSION['counter'] = 1;
} else {
    $_SESSION['counter']++;
}

echo "You have visited this page " . $_SESSION['counter'] . " times during this session.";
?>

Important Notes

Sessions use cookies by default to keep track of users.

Always call session_start() at the very top of your PHP file before any output.

Session data is stored on the server, so it is safer than passing data in URLs.

Summary

Sessions let you save user data across multiple pages.

Always start a session with session_start() before using $_SESSION.

Use sessions to keep users logged in or remember their choices.