Cookie expiration

Learn to set a cookie's lifetime by passing an expiration to setcookie().

Expiration and time()

By default a cookie lives until the browser closes. Give it an expiration and it lives longer. The third argument to setcookie() is a Unix timestamp.

time() returns the current timestamp in seconds (since 1 Jan 1970). Add seconds to compute a future date: time() + 3600 is one hour ahead.

Example: setcookie('lang', 'en', time() + 86400) keeps the cookie for 24 hours.

Persistent cookies

A cookie with a third argument is persistent: it survives on disk until the expiration, even if the browser is closed. This is ideal for user preferences (language, theme).

Without an expiration the cookie is a session cookie: deleted when the browser window closes. This suits temporary state.

A past expiration makes the browser delete the cookie immediately; we use this for deletion.

Exercise Create a one-week cookie

Call setcookie() with name 'prefs', value 'dark', and expiration time() + 604800 (one week). Then echo set.

Show example solution

Call setcookie('prefs', 'dark', time() + 604800), then echo "set".
Example solution:
<?php
// Create the 'prefs' cookie with a 1-week expiration
setcookie('prefs', 'dark', time() + 604800);
echo "set\n";

Test yourself

Add a one-hour expiration

<?php
$cfg = ['name' => 'token', 'value' => 'abc'];
setcookie($cfg['name'], $cfg['value'], ____);
echo 'set';

Show answer

<?php
$cfg = ['name' => 'token', 'value' => 'abc'];
setcookie($cfg['name'], $cfg['value'], time() + 3600);
echo 'set';

What does time() return?
- Seconds since 1 January 1970
- Current date in YYYY-MM-DD format
- The cookie's expiration
- A duration in microseconds
Show answer

Seconds since 1 January 1970 — Correct. time() returns the Unix timestamp in seconds.
Match the duration expressions

time() + 3600

1 hour
time() + 86400

1 day
time() + 604800

1 week
time() + 31536000

1 year

Next lesson: Deleting cookies

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