Difference Between Cookies and Session

Both cookies and sessions remember information about a visitor, but they keep it in different places.

	Cookie	Session
Stored in	The visitor browser	The server
Size limit	About 4 KB	No fixed limit (depends on the server)
Visible to the user	Yes, the user can read and change it	No, only the session id is in the browser
Lifetime	Until the expiry date you set	Until the browser is closed or the session expires (about 24 minutes of inactivity by default)
Best for	Small, harmless data: theme, language, “remember me” token	Private data: login status, user id, shopping cart
PHP array	$_COOKIE	$_SESSION

A session actually uses a cookie too, but only for the session id (called PHPSESSID). PHP uses that id to find the real data on the server. So the private data never goes to the browser.

<?php
// Cookie: stored in the browser
setcookie("theme", "dark", time() + 3600);

// Session: stored on the server
session_start();
$_SESSION["user_id"] = 25;
?>

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Difference Between Cookies and Session