# How to use PHP Cookie-based Sessions

> Learn how to use cookie-based sessions in PHP with session_start, store data server-side in $_SESSION, and clear it with session_unset.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2022-09-01 | Topics: [PHP](https://flaviocopes.com/tags/php/) | Canonical: https://flaviocopes.com/php-sessions/

One very interesting use case for cookies is cookie-based sessions.

PHP offers us a very easy way to create a cookie-based session using `session_start()`.

Try adding

```php
<?php
session_start();
?>
```

in a PHP file, and load it in the browser.

You will see a new cookie named by default `PHPSESSID` with a value assigned.

That’s the session ID. This will be sent for every new request and PHP will use that to identify the session.

![Browser developer tools showing PHPSESSID cookie created by session_start function](https://flaviocopes.com/images/php-sessions/Screen_Shot_2022-06-27_at_14.51.53.jpg)

Similarly to how we used cookies we can now use `$_SESSION` to store the information sent by the user, but this time it’s not stored client-side.

Only the session ID is.

The data is stored server-side by PHP.

```php
<?php
session_start();

if (isset($_POST['name'])) {
  $_SESSION['name'] = $_POST['name'];
}
if (isset($_POST['name'])) {
  echo '<p>Hello ' . $_POST['name'];
} else {
  if (isset($_SESSION['name'])) {
    echo '<p>Hello ' . $_SESSION['name'];
  }
}
?>

<form method="POST">
  <input type="text" name="name" />
  <input type="submit" />
</form>
```

![Web page showing Hello test message with PHPSESSID cookie visible in browser developer tools](https://flaviocopes.com/images/php-sessions/Screen_Shot_2022-06-27_at_14.53.24.jpg)

This works for simple use cases, of course for intensive data you will need a database.

To clear the session data you can call `session_unset()`.

To clear the session cookie use:

```php
setcookie(session_name(), '');
```